Inequality in the Distribution of Income: Trends and International Comparisons

Inequality in the Distribution of Income: Trends and International Comparisons

Inequality in the Distribution of Income:
Trends and International Comparisons
Brian W. Cashell
Specialist in Macroeconomic Policy
October 19, 2009
Congressional Research Service
7-5700
www.crs.gov
RL32639
CRS Report for Congress
P
repared for Members and Committees of Congress

Inequality in the Distribution of Income: Trends and International Comparisons

Summary
Economic theory alone does not establish any basis for preferring a more or less equal
distribution of income. Nonetheless, a common aim of policy is promoting equality of
opportunity. An extremely unequal distribution of income may be considered an indication of a
lack of equal opportunity. Arguments for a more equal distribution of income than that which
would result from market forces are based on a number of propositions. One is a common
assumption made in economic analysis known as diminishing marginal utility of income. This is
the notion that each additional dollar of income yields less utility, or satisfaction. If the
assumption of diminishing marginal utility of income is accepted, then, in theory, it should be
possible to increase the overall well-being (utility) of society by taking some from those with
high incomes and giving it to those with low incomes. A second, non-economic, justification for
policies designed to make the income distribution more equal is concern that society prevent its
members from falling below some minimum standard of living.
Existing measures of income fall well short of an ideal that would accurately indicate how well
off individuals or households are. Not all kinds of income are counted. Taking the existing
measures at face value, however, several observations can be made. First, the distribution of
income in the United States has become increasingly unequal since the late 1960s. Second, the
U.S. income distribution is one of the most unequal of all major industrialized countries. Some of
the greater income equality found in other major industrialized countries may be due to the fact
that government transfers are more directly targeted at lower income households.
The distribution of earnings is more unequal than is the distribution of household income. Of
particular interest is that the gap in earnings between highly educated or skilled workers and less
skilled workers has grown substantially. Explanations focusing on world trade and national
demographics have been suggested, but the one most widely accepted is that technological
advances in recent years have increased the demand for more highly skilled labor relative to its
supply. Policies that boost the supply of skilled workers would thus seem likely to narrow that
gap and act as an equalizing influence on the income distribution. But, the large gap in pay
between skilled and unskilled workers that has developed would itself seem to be a substantial
incentive for prospective and current workers to expand their education and training.
This report will be updated as developments warrant.

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Inequality in the Distribution of Income: Trends and International Comparisons

Contents
Evaluating Distributions.............................................................................................................. 1
Measuring Income ...................................................................................................................... 2
Measuring Inequality .................................................................................................................. 3
International Comparisons of Income Distributions ..................................................................... 7
Explaining International Differences ..................................................................................... 9
Explaining Recent Trends ......................................................................................................... 10
Conclusions and Policy Considerations ..................................................................................... 14

Figures
Figure 1. Distribution of Household Income: 1968 and 2008 ....................................................... 5
Figure 2. Household Income Gini Index, 1968-2008.................................................................... 6

Tables
Table 1. Distribution of Household Income by Quintile ............................................................... 4
Table 2. Summary Measures of Income Distributions for Selected Countries ............................... 8

Contacts
Author Contact Information ...................................................................................................... 15

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Inequality in the Distribution of Income: Trends and International Comparisons

n economic contraction began in December 2007. The consequent decline in incomes and
rise in unemployment has increased existing concerns about a long-term trend of growing
A inequality in the distribution of income. There is no shortage of anecdotal evidence
regarding workers who are losing ground in a weak economy; however, even when the economy
was growing, the benefits did not seem to be shared by all.
There are a number of legislative issues for which the shape of the income distribution may be an
important consideration. Among them are tax rates, the minimum wage, and the allocation of
various benefits. This report examines the distribution of income in the United States, including
factors that may help explain it, how it has changed over time, and how it compares with those of
other countries.
Evaluating Distributions
Economic theory gives no basis for preferring any particular degree of equality in the distribution
of income. In theory, at least with respect to labor income, what matters is that the distribution
result from efficient markets where final demand for goods and services and the relative
productivity of the firms producing those goods and services determine the demand for labor in
each sector of the economy, and the earnings of each of those jobs.
The shape of the income distribution is also a function of labor supply. The willingness of
workers to take jobs depends on pay as well as relative preferences for labor and leisure. The
ability of workers to command a given wage is also a direct function of their educational
attainment and skill level (their “human capital”). Changes in the age distribution can also affect
the income distribution as workers tend to earn more as they get older, and gain more experience.
Even in an economically “ideal” world, however, where the income distribution was solely
attributable to the workings of efficient markets there may still be moral, ethical, or philosophical
reasons for preferring an alternative outcome.
Arguments for a more equal distribution of income than that which results from market forces are
based on a number of propositions.1 One is founded on a common assumption made in economic
analysis known as diminishing marginal utility of income. This refers to the idea that each
additional dollar of income yields less and less satisfaction (in economic jargon, utility) than the
first. Put another way, this proposition presumes that one additional dollar of income means less
to someone making $100,000 than it does to someone making $20,000.
If the assumption of diminishing marginal utility of income has merit, then in theory it should be
possible to increase the overall well-being (utility) of society by taking money from those with
high incomes and giving it to those with low incomes. In other words, the loss in utility for those
with high incomes is less than the gain in utility for those with low incomes. The difficulty with
that proposition is that doing that may have economic costs that offset part, if not all, of any net
gain in overall utility.
A second justification for policies designed to make the income distribution more equal is
concern that society prevent its members from falling below some minimum standard of living.

1 See N. Gregory Mankiw, Principles of Economics (Fort Worth Texas: The Dryden Press, 1998).
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Inequality in the Distribution of Income: Trends and International Comparisons

This may be due to pure altruism, or the sense that luck has something to do with one’s place in
the income distribution, or the belief that when more people have a stake in society, the more
tranquil it will be. Raising the minimum standard of living may thus serve as a kind of insurance.
Finally, a common goal of policy is promoting equality of opportunity. An extremely unequal
distribution of income may be considered an indication of lack of equal opportunity.
Beyond these considerations, economics has little to say about the desirability of any particular
income distribution, but economists have developed ways to measure changes in the distribution,
and have searched for causes of variations in the distribution over time.
Measuring Income
As is the case with any number of economic statistics, income data have limitations. The Census
Bureau, in an annual survey, collects data based on the concept of money income. Money income
accounts for a wide range of income sources, but it is unavoidably incomplete. Money income
includes income from earnings, interest and dividends, Social Security, and other forms of social
insurance. It does not include the value of non-money benefits such as food stamps or housing
subsidies, nor does it include capital gains.2
With respect to the distribution of overall economic well-being, a limited measure such as money
income may be misleading. For example, consider the case where two families are in every way
equal in terms of wealth and income, neither owns their home, but they both have substantial
savings in interest earning assets. Suppose one family takes funds that are earning interest and
uses them to buy their home. No one would argue that that family is now worse off, but the
existing measures of money income would indicate that to be the case. In fact, the family that
buys its home is earning an implicit income in the use of the house just as they would earn rental
income if they rented it to the other family in the example. Not counting this implicit income in
existing measures may have a significant effect on the shape of the distribution. If
homeownership rates change over time, or the share of assets invested in owner-occupied housing
changes, and those changes affect one part of the distribution more than another, then existing
data concerning changes in the shape of the distribution of income would be misleading.
Existing measures of income also ignore the value of leisure. Thus, in the case of two individuals
whose measured incomes differ only because one of them works longer hours, the difference in
their incomes may overstate the difference in their economic well-being because the one who is
working longer hours is sacrificing leisure time.
Another weakness in existing measures of income is that they do not account for the implicit
income yielded by homemakers or other work done at home. Consider two different married-
couple households with the same income and both husband and wife are working. If in one of the
households, the husband quits his job to stay at home and raise children, that household will
experience a drop in money income. But the work done at home is not without value, and the
measured difference in the incomes of the two households will overstate the difference in their
living standard.

2 For a complete explanation of what is included in money income, see U.S. Department of Commerce, U.S. Census
Bureau, Current Population Reports: Consumer Income, Series P60-231, August 2006, Appendix A.
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The time period in which income is measured may also affect comparisons in the economic well-
being of different households. Over the course of the business cycle, unemployment rises and
falls and so do incomes. Some households may tend to be more affected than others by these
cycles, and so the stage of the business cycle can have a significant effect on relative incomes.
Similarly, individuals’ incomes generally vary substantially over the course of their lifetimes.
New entrants to the labor force typically have lower incomes than those who have been working
for some time. After retirement, income tends to drop off. Because of changes in income
associated with this life cycle, the demographic mix of the population can have a major influence
on measures of income disparity.
If it is concern about living standards that prompts interest in the distribution of income, then
changes in wealth (e.g., the value of real estate, or other components of net worth) might also be
taken into account. The allocation of household assets can also make a difference. Investments
that yield interest and dividends will add to measured income, but investment returns in the form
of appreciation will not.
Another difficulty in comparing incomes is deciding what is the relevant population. In the case
of labor income, the distribution of income among working age individuals or among those that
are employed may be of most interest. But when it comes to overall living standards, it may be
more appropriate to consider the distribution of income among households. Most households can
be presumed to pool resources and enjoy some economies of scale. In other words, because some
costs of living are fixed, a family of four may not need twice as much income as a married couple
for each family member to enjoy roughly the same living standard. That adds another
complication in comparing incomes for households of different sizes.
Measuring Inequality
For the sake of simplicity and clarity, one way the Census Bureau publishes income distribution
data is by “quintile.” Households are ordered from lowest income to highest, and then divided
into five groups of equal size. The income within each group is summed and then compared to the
total income of the population. If income were all equally divided and every household had the
same income, then each quintile would account for 20% of total income. To the extent that each
quintile falls short of, or exceeds, a 20% share, it is an indication of the degree of inequality in the
distribution.
Table 1 presents data on the share of total household money income accounted for by each
quintile, as well as for the top 5%, since 1968. The figures indicate that the bottom fifth accounts
for much less than the one-fifth of total income it would get if the distribution were perfectly
equal, while the top 20% accounts for more than twice what it would get in an equal distribution.
The top 5% accounts for more than four times the 5% share it would get if the distribution were
perfectly equal.
There are also several trends evident at the two ends of the distribution. Between 1968 and 1978,
there was a modest decline in the share of income accounted for by the middle 60% of the
distribution and an increase in the share accruing to those households in the top 20%. Since 1980,
however, the share accruing to the bottom fifth has fallen, and the shares accounted for by both
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Inequality in the Distribution of Income: Trends and International Comparisons

the top 20% and the top 5% have risen. Between 1968 and 2008, the share of income accounted
for by the three middle quintiles fell from 54.2% to 46.6%.3
Table 1. Distribution of Household Income by Quintile

Percentage Share of Total Household Income

Bottom
Second
Third
Fourth
Fifth
Top 5%
1968 4.2 11.1
17.6
25.5
42.6
16.3
1978 4.2 10.2
16.8
24.7
44.1
16.8
1980 4.2 10.2
16.8
24.7
44.1
16.5
1990 3.8 9.6
15.9
24.0
46.6
18.5
2000 3.6 8.9
14.8
23.0
49.8
22.1
2001 3.5 8.7
14.6
23.0
50.1
22.4
2002 3.5 8.8
14.8
23.3
49.7
21.7
2003 3.4 8.7
14.8
23.4
49.8
21.4
2004 3.4 8.7
14.7
23.2
50.1
21.8
2005 3.4 8.6
14.6
23.0
50.4
22.2
2006 3.4 8.6
14.5
22.9
50.5
22.3
2007 3.4 8.7
14.8
23.4
49.7
21.2
2008 3.4 8.6
14.7
23.3
50.0
21.5
Source: U.S. Department of Commerce, U.S. Census Bureau.
A second indicator of the relative degree of inequality in the distribution of income is the Gini
index, also known as the index of income concentration. The Gini index is a single number which
can range between zero and one. It is an index, and therefore is not expressed in terms of any
particular unit of measurement, but it allows comparisons between and among distributions. They
can be distributions from two different populations, or of the same population at different points
in time. Thus, it can show if one distribution is more or less equal than another, and if there is any
tendency for one distribution to become more or less equal over time.
To illustrate how the Gini index is calculated, Figure 1 shows the distribution of household
income for both 1968 and 2008. The horizontal axis represents the cumulative share of
households, beginning at the low end of the distribution and working up to the household with the
highest income. The vertical axis represents the cumulative share of income accounted for by
those households.

3 There is no official definition of the “middle class.” For further discussion, see CRS Report RS22627, Who Are the
“Middle Class”?, by Brian W. Cashell.
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Inequality in the Distribution of Income: Trends and International Comparisons

Figure 1. Distribution of Household Income: 1968 and 2008
100
80
line of perfect equality
me
co
n
60
f i
t o
1968
40
rcen
e
p
20
2008
0
0
20
40
60
80
100
percent of households

Source: Department of Commerce, Bureau of the Census.
The curved lines in Figure 1 represent actual distributions of household income. (These are also
known as ‘Lorenz’ curves.) The straight diagonal line shows what the distribution would look like
if it were perfectly equal, in other words if each household had the same income (e.g., with 100
households each household would account for 1% of total household income). The more equal
the actual distribution is, the closer the line is to the hypothetical diagonal.
The Gini index is a ratio of the area between the diagonal and the line representing the actual
distribution, and the total area under the diagonal. The closer the actual distribution is to the
hypothetical equal distribution, the smaller the area will be between the two lines. If the actual
distribution and the diagonal coincide, then the Gini is zero, indicating a perfectly equal
distribution of income. In that case, each household would have identical incomes.
At the other extreme, consider a distribution where all income accrued to a single household. In
that case, the actual curve would lie on the edge of the graph and the Gini index would be one. An
increasing Gini index number indicates an increasingly unequal distribution. When comparing
any two distributions, the one described by a higher Gini index number is the more unequal.
Between 1968 and 2008, the actual distribution moved further away from the hypothetical equal
distribution and the Gini index rose, indicating that the distribution of household income has
become more unequal. Figure 2 plots the Gini index for the distribution of household income in
the United States since 1968.
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Figure 2. Household Income Gini Index, 1968-2008
0.48
0.47
0.46
0.45
0.44
0.43
0.42
0.41
0.40
0.39
0.38
1968
1972
1976
1980
1984
1988
1992
1996
2000
2004
2008

Source: Department of Commerce, Bureau of the Census.
Over the period shown, the trend has been one of almost steadily increasing household income
inequality. The index is now below the peak reached in 2006, but still indicates a distribution that
is much more unequal than it has been for most of the years for which data are available.
In addition to the Gini index, there are other summary measures that describe changes in the
income distribution. Among those measures are ratios of incomes at different points in the
distribution. For example, the ratio of the income of those at the 90th percentile in the distribution
to that of those in the 10th percentile gives an estimate of the overall inequality in a distribution.
Similarly, the ratio of the median income level (50th percentile) to the 10th percentile income level
and the ratio of the 90th percentile income level to the median income can be computed. Changes
in those ratios may indicate whether a change the degree of inequality is due to changes at the top
or at the bottom of the distribution.
Economists at the Federal Reserve Bank of Richmond examined changes in those ratios to shed
some light on changes in the distribution.4 They found that, between 1961 and 2002, 75% of the
increase in the 90-10 income ratio was accounted for by the increase in the 90-50 income ratio. In
other words, changes in the upper half of the income distribution accounted for most of the
overall increase in inequality. The authors also examined changes in the distribution of the top
10% of the distribution. Between 1961 and 2003, the share of labor income accruing to the top
10% rose from 27% to 37%, and more than 60% of that increase in share was attributable gains in
the top 1% of the distribution. Moreover, the authors found that more than 60% of the gains in the
income share of the top 1% was due to an increased share going to the top 0.1%.

4 Kevin A. Bryan and Leonardo Martinez, “On the Evolution of Income Inequality in the United States,” Economic
Quarterly, Federal Reserve Bank of Richmond, spring 2008.
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Inequality in the Distribution of Income: Trends and International Comparisons

Thus far, the only measures considered have been cross sections of the income distribution at
fixed points in time. But those do not indicate how many of the households in, say, the bottom
20% of the distribution in one year are still there in the next. How a given household assesses its
position in the overall distribution may depend on its prospects for moving either up or down in
it. Those households near the bottom of the distribution who do not expect to stay there may have
fewer concerns with overall inequality than those who do.
A study published by the Federal Reserve Bank of Boston found that family income mobility
declined between 1967 and 2004.5 The authors examined income by decile and found that income
mobility made the long-run distribution of income more equal than it is at any single point in
time. The decline in mobility, however, means that it has become less and less likely that families
that begin near the bottom of the distribution will be able to escape. The authors leave it an open
question whether the decline in mobility can be attributed to rising barriers to opportunity or is
simply the result of changes in the labor market.
International Comparisons of Income Distributions
In addition to tracking changes in inequality over time, international comparisons of the
distributions of income may also put domestic measures in perspective. But, just as available
measures of income in the United States differ from the ideal, measures of income in different
countries also differ from each other. There is, however, a source for comparable data that allows
international comparisons of income inequality.
The Luxembourg Income Study (LIS) project has assembled survey data from a large number of
different countries’ statistical programs on social and economic indicators.6 Among those
statistics available are data on household income. Although there are differences in individual
definitions of income across countries, these data can be adjusted so that they reflect a more
consistent measure of income.
In making these adjustments to get to a common measure of income, however, the definition of
income had to be limited. In limiting what is counted as income, the actual measures that allow
cross-country comparisons are in some cases more removed from the ideal measure than they
might otherwise be.
The LIS uses a measure of after-tax household money income as its standard.7 This necessarily
excludes the imputed values for owner-occupied housing and unpaid homework. It does include
some “near cash” subsidies such as food stamps, housing subsidies, and certain scholarships.
Income is also measured net of income and payroll taxes but not of sales, value added, and other
indirect taxes. That may make the distributions seem more equal in those countries that rely
heavily on income taxes, which tend to be progressive.

5 Katharine Bradbury and Jane Katz, “Trends in U.S. Family Income Mobility, 1967-2004,” Federal Reserve Bank
Bank of Boston Working Paper no. 09-7, August 2009.
6 Information about the Luxembourg Income Study can be found at their website, at http://www.lisproject.org.
7 Peter Gottschalk and Timothy M. Smeeding, Empirical Evidence on Income Inequality in Industrialized Countries,
Luxembourg Income Study Working Paper No. 154, revised February 1999.
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Inequality in the Distribution of Income: Trends and International Comparisons

The standard of living afforded to a household by a given amount of income is also affected by
the size of the household. An adjustment is made to these household income data to reflect the
fact that the income must be divided among the members of the household. The LIS study
assumes that there are some economies of scale and that each additional member of a household
requires a slightly smaller amount of income to maintain the overall standard of living of the
household.
The LIS reports data allowing direct comparisons of income distributions of a large number of
different industrialized countries. Table 2 presents summary data on the income distribution from
some of them. The countries are listed in order from the one with the lowest Gini index number
(most equal distribution) to the one with the highest (most unequal distribution).
The first column of data shows the estimated Gini coefficient for each country. The next column
(P90/P10) shows the ratio of the incomes of those at the 90th percentile of the distribution to the
incomes of those at the 10th percentile. For example, for the United States in 2004, those near the
top of the distribution had more than five times the income as those near the bottom. The last
column (P90/P50) indicates the ratios of income at the 90th percentile of each distribution to the
median incomes (the 50th percentile) of that distribution. For the United States, those at the 90th
percentile in the distribution had more than twice the U.S. median income. Note that the data are
from different years so that, to some extent, differences between countries may be attributable to
the effects of the business cycle.
Table 2. Summary Measures of Income Distributions for Selected Countries
Country Year
Gini
Index
P90 /P10
P90 /P50
Denmark 2004
0.228
2.78
1.56
Netherlands 1999
0.231
2.78
1.63
Sweden 2005
0.237
2.82
1.63
Norway 2004
0.256
2.87
1.60
Germany 2000
0.275
3.37
1.80
France 2000
0.278
3.45
1.88
Belgium
2000
0.279
3.30
1.74
Australia 2003
0.312
4.24
1.98
Canada 2004
0.318
4.38
1.96
Italy 2000
0.333
4.47
1.99
United Kingdom
2004
0.345
4.46
2.14
United States
2004
0.372
5.68
2.13
Russia 2000
0.434
8.37
2.76
Mexico 2004
0.458
8.48
2.98
Source: Luxembourg Income Study.
A study by Atkinson, Rainwater, and Smeeding, using LIS data from the late 1970s, found that
most of these countries had experienced an increase in the degree of inequality in their income
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distributions, with the largest increases in the United States and the United Kingdom. That at least
suggests the possibility of some common factor influencing the distributions of these economies 8
.
However, Smeeding also points out that over the last 25 years, the United States started with the
most unequal distribution among the rich nations of the world and over that period experienced
the largest increase in inequality of those rich nations 9
.
Although the United States appears to have a relatively unequal distribution, the median income
in the United States is higher than in other countries. Smeeding and Rainwater analyzed income
at different points in the distributions and made adjustments for differences in the purchasing
power of the different currencies.10 They found that people in the upper half of the distribution in
the United States enjoyed living standards far above their counterparts in other industrialized
countries. However, those near the bottom, at the 10th percentile in the U.S. distribution, were not
as well off as those at the same point in the distribution in the other countries examined.
Explaining International Differences
What explains these international differences in income distributions? The reasons fall into three
categories. First, many other countries devote a much larger share of their national output to
income transfers, which have an equalizing effect on the distribution. Second, these data are
based on income after taxes, and tax rates in these countries vary with respect to progressivity,
and thus have different effects on the equality of the distribution of after tax income. Third,
equality in the distribution of earnings, which account for about 70% of household income in the
studies using LIS data, varies substantially as well.
For those countries for which data are available, there is a strong correlation between income
shares at the lower end of the distribution and the share of GDP accounted for by transfer
payments.11 The evidence suggests, however, that for both the United States and Britain, given the
amount of money that is transferred, those at the low end of the distribution do not benefit as
much as they do in other countries.
Although taking into account taxes and transfers may affect cross-country comparisons of income
inequality, for year-round full time workers the United States also exhibits relatively greater
inequality in the distribution of earnings.
One explanation for the greater equality in earnings distributions abroad is that wage-setting tends
to be more centralized in many other countries than it is in the United States. There are two
reasons for this. First, in the private sector, union membership may be higher, and in some cases
there is a considerable share of the labor force that is affected by union agreements whether they
are union members or not. Second, in a number of these countries, the public sector also accounts

8 Anthony B. Atkinson, Lee Rainwater, and Timothy M. Smeeding, Income Distribution in OECD Countries: Evidence
From the Luxembourg Income Study, Organisation for Economic Co-operation and Development, 1995.
9 Timothy M. Smeeding, Public Policy and Economic Inequality: The United States in Comparative Perspective,
Luxembourg Income Study Working Paper No. 367, February 2004.
10 Timothy M. Smeeding and Lee Rainwater, Comparing Living Standards Across Nations: Real Incomes at the Top,
the Bottom and the Middle, Luxembourg Income Study Working Paper No. 266, May 2001.
11 Timothy M. Smeeding, “U.S. Income Inequality in a Cross-National Perspective: Why Are We So Different?,”
Looking Ahead, National Policy Association, vol. XIX, no. 2-3.
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for a greater share of employment than in the United States, and that serves as an equalizing
force.12
A study published by the Chicago Federal Reserve Bank examined income inequality in five
countries: the United States, Canada, Germany, Sweden, and Finland.13 The study found that, after
taxes and transfer payments, the U.S. income distribution was the most unequal of the five,
followed by Canada, Germany, Finland, and Sweden. Of those countries, Germany did relatively
little to redistribute income, either through taxes or transfers, but it had the most equal
distribution of labor income. Sweden and Finland reduced income inequality through a
combination of relatively high tax rates and high levels of transfer payments. Canada and the
United States reduced income inequality with similar combinations of progressive income taxes
and transfer payments.
To the extent that greater equality in the income distribution is a result of deliberate policy and
not the result of market forces, that equality may not have been achieved without some cost.
Assuming that these costs are appreciated, they may reflect varying degrees of willingness in
different countries to tolerate inequality in the distribution of income.
Explaining Recent Trends
Most industrialized countries have, and certainly the United States has, experienced an increase in
the degree of inequality in the distribution of income. More specifically, most countries have
experienced an increase in the inequality of earnings. Those studies that focus more narrowly on
wages have come to similar conclusions.
Two explanations are often cited for the trend toward greater inequality. The first has to do with
trade liberalization (“globalization”), and the second has to do with technological progress.
With regard to trade liberalization, the argument is that because of reduced trade restrictions and
an increasing volume of trade, less skilled U.S. workers have become more vulnerable to direct
competition from lower paid workers in other countries. Thus, the production of goods that
require less-skilled workers has shifted overseas and the domestic demand for less-skilled
workers has declined here. The reduced demand for less-skilled workers in manufacturing here
has placed downward pressure on their wages, and therefore tended to increase the earnings gap
between skilled and unskilled workers.
Whether that is the case is not completely settled, but the hypothesis has not been accepted by
most economists. Although theoretically sound, the argument has not yet been supported by
compelling empirical evidence. For one thing, the wage gap between skilled and unskilled
workers has grown both in those industries that tend to compete in world markets as well as those
that are generally less affected by international trade. Another reason economists have not found

12 See Gottschalk and Smeeding, “Cross-National Comparisons of Earnings and Income Inequality,” Journal of
Economic Literature, vol. XXXV (June 1997).
13 Mariacristina De Nardi, Liqian Ren, and Chao Wei, “Income Inequality and Redistribution in Five Countries,”
Federal Reserve Bank of Chicago Economic Perspectives, Second Quarter 2000, vol. XXIV, issue 2.
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the trade argument convincing is that the number of jobs affected by the increase in trade is not
sufficient to explain the magnitude of the earnings gap economy wide.14
The argument that changes in technology have affected the distribution of earnings has been more
persuasive among many economists. The most often cited evidence for such an effect is the rapid
growth in the wage premium paid to more highly skilled or educated workers that began in 1979.
In 1979, men with bachelor’s degrees earned 50% more than did those with a high school
education. For women, the college premium in 1979 was 41%. In 2008, the advantage of a
college education was significantly higher, with college-educated men and women earning, on
average, 90% and 77% more, respectively, than those with a high school education. Further, that
increased advantage coincided with a significant increase in the proportion of the labor force that
was college educated, from 16.4% of adults in 1979 to 28.7% in 2007, according to the Census
Bureau. Even though the supply of more highly educated workers was rising, it was apparently
not rising fast enough to keep up with increasing demand.15
One theory behind these numbers is that technological changes over the past 20 years have not
affected all jobs equally. The argument is that the kinds of technological advances that have
occurred since the late 1970s have been biased in favor of those jobs that require higher levels of
training and education.
Not all advances require more educated workers to exploit them. Retail clerks may no longer
need to be as proficient at math and some assembly line jobs may have become simpler and more
repetitive. But the evidence suggests that demand for more highly educated workers has increased
substantially. Further, those who use computers in their work have experienced relatively larger
wage gains than have other occupations. The wage gap between less and more highly educated
workers has also been found to be correlated with rising outlays on research and development.16
The case for “biased” technological change explaining increased income inequality has gained
wide acceptance among economists. Autor, Levy, and Murnane published a study suggesting that
technological progress affected the equality of the earnings distribution in two ways.17 First,
information technology (IT) served as a substitute for low-skill workers reducing demand for
their labor. Second, IT served as a complement to educated and relatively high-skilled workers
increasing demand for their services. Both factors appear to have contributed to an increase in
inequality in the distribution of earnings.
A study published by the Bureau of Labor Statistics examined wage data and found that those
occupations that had relatively high wages in 2002 experienced relatively more rapid wage
growth between 2002 and 2008.18 The authors also found that, between 2002 and 2008, those

14 See Gary Burtless, “International Trade and the Rise in Earnings Inequality,” Journal of Economic Literature, vol.
XXXIII (June 1995).
15 Peter Gottschalk, “Inequality, Income Growth, and Mobility: The Basic Facts,” Journal of Economic Perspectives,
vol. 11, no. 2, spring 1997.
16 Gary Burtless, “Technological Change and International Trade: How Well Do They Explain the Rise in U.S. Income
Inequality?” Looking Ahead, National Policy Association, vol. XIX, no. 2-3. See also U.S. Department of Commerce,
U.S. Census Bureau, Money Income in the United States: 1998, Series P60-206, September 1999.
17 David Autor, Frank Levy, and Richard Murnane, “The Skill Content of Recent Technological Change: An Empirical
Exploration,” NBER Working Paper 8337, June 2001.
18 John I. Jones, “What do OES Data Have to Say About Increasing Wage Inequality?,” Monthly Labor Review, June
2009.
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occupations typically associated with higher skills and education levels experienced more rapid
wage growth than those that were not.
Some trends in the labor market do not easily fit in the skill-biased technological change
hypothesis. Card and DiNardo examined the data to see how well events agreed with the
implications of skill-biased change.19 They found a number of contradictions. For example, the
biased change hypothesis would seem to predict that groups that typically have lower skills would
have experienced relatively slower wage growth. Card and DiNardo argue that although women
tend to be less skilled on average than men, and that nonwhite workers tend to be less skilled than
white workers, those two groups did not experience slower wage growth and the wage gaps
between groups did not widen as the theory might have predicted. The authors also found that the
wages of college graduates with degrees in the humanities grew more rapidly than the wages of
graduates with degrees in engineering or science.
A study published by the Federal Reserve Bank of Minneapolis examined the changing
distribution of earnings since 1961.20 Eckstein and Nagypál found that, for men, there was a
substantial increase in the inequality of the earnings distribution beginning in the mid-1970s.
Between 1973 and 1995, the real earnings of men in the bottom 25% of the earnings distribution
fell. Over that same period, the real earnings of men in the top 25% of the distribution made
significant gains. They also found that beginning in 1995, the year productivity growth picked up,
the real earnings of men in the bottom 25% of the distribution began to rise along with earnings
all across the distribution. However, the earnings of men at the top of the distribution grew more
rapidly. While the distribution continued to grow more unequal after 1995, the rate of increase in
that inequality slowed. Women’s earnings exhibited similar although less pronounced changes in
inequality.
A study by the Kansas City Federal Reserve Bank examined the connection between productivity
growth and income growth.21 The authors found that between 1974 and 1995 only the top quintile
(the 20% with the highest incomes) in the income distribution experienced income growth equal
to the growth rate of productivity. Between 1995 and 2005, the authors found, even the top
quintile in the distribution experienced income growth below the rate of productivity increase.
They point out that limitations of the survey on which those data are based make it difficult to
identify trends at the upper end of the income distribution.
Dew-Becker and Gordon examined the relationship between labor income and productivity and
concluded that the benefits of productivity growth have been unequally distributed.22 Dew-Becker
and Gordon looked at Internal Revenue Service (IRS) income data from 1966 to 2001. They
concluded that over that entire period, only the top 10% of the distribution experienced income
gains equal to or greater than the overall rate of productivity growth. Further, they found that the
top 1% of the distribution accounted for 21.6% of the income gains for that period and for 21.3%
of the gains between 1997 and 2001, after productivity growth had accelerated. Finally, they

19 David Card and John E. DiNardo, “Skill-Biased Technological Change and Rising Wage Inequality: Some Problems
and Puzzles,” Journal of Labor Economics, vol. 20 no.4 2002.
20 Zvi Eckstein and Éva Nagypál, “The Evolution of U.S. Earnings Inequality: 1961-2002,” Federal Reserve Bank of
Minneapolis Quarterly Review, December 2004.
21 Jonathan L. Willis and Julie Wroblewski, “What Happened to the Gains From Strong Productivity Growth?,” Federal
Reserve Bank of Kansas City, Economic Review, First Quarter 2007.
22 Ian Dew-Becker and Robert J. Gordon, Where Did the Productivity Growth Go? Inflation Dynamics and the
Distribution of Income, National Bureau of Economic Research Working Paper 11842, December 2005.
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found that the top 0.1% of the distribution received as much of the real rise in earnings as the
bottom 50% between 1997 and 2001.23 The authors suggest that some of this is may be due to the
expansion of opportunities available to “economic superstars” such as sports stars and other top
celebrities because of technologies such as cable television and the Internet.
Saez found that the share of income accounted for by the very top of the distribution has been
increasing in recent years. Using Internal Revenue Service data he found that between 2006 and
2007, the income of those in the top 1% and in the top 0.1% grew more rapidly than average
income. The share of family income accounted for by the top 1% of the distribution rose from
22.8% to 23.5% between 2006 and 2007, and the share accounted for by the top 0.1% grew from
5.46% to 6.04% over the same period.24
Although the effects of trade liberalization and technological growth are the two most often
discussed factors which might explain the increase in inequality, there are other factors at work in
the changing shape of the household income distribution.
Shifting demographic factors have also played a role. One of the most important shifts has been
the large rise in the labor force participation of women. Specifically, there has been a substantial
increase in the number of households with working wives. In 1970, just over half of all married
mothers had some work experience during the year. In 2005, that proportion had risen to 66%.
The share of married mothers who worked full time rose from 16% to 47% over the same
period.25
In those families with working wives, their contribution to family income has been growing.26
Traditionally, wives’ earnings tend not to be highly correlated with their husbands’ earnings, part
of which is due to the negative correlation between husbands earnings and wives’ labor force
participation. Thus, the distribution of husbands’ earnings has been less equal than is the
distribution of total household earnings. However, during the period studied wives’ earnings
became more highly correlated with their husbands’ earnings, and that has been a factor in the
rising inequality in the distribution of household income.27
Changes in the distribution of wealth may also have had an effect on the income distribution over
time. The distribution of household wealth is more unequal than is the distribution of either
earnings or total income.28
An analysis by Burtless attempted to identify the proximate causes of the increase in inequality.
By controlling for both changes in earnings inequality and changes in the composition of

23 Aside from the direct effects of productivity on earnings Dew-Becker and Gordon found that the acceleration in
productivity contributed to a 1.2% slower rate of inflation between 1995 and 2005. That meant an increase in the
purchasing power of all workers.
24 Emmanuel Saez, “Striking it Richer: The Evolution of Top Incomes in the United States (Update with 2007
estimates,” August 5 2009, available on the web at http://elsa.berkeley.edu/~saez/saez-UStopincomes-2007.pdf.
25 Howard V. Hayghe and Suzanne M. Bianchi, “Married Mother’s Work Patterns: The Job-Family Compromise,”
Monthly Labor Review, June 1994.
26 Howard V. Hayghe, “Working Wives’ Contribution to Family Incomes,” Monthly Labor Review, August 1993.
27 Peter Gottschalk and Timothy Smeeding, “Cross-National Comparisons of Earnings and Income Inequality,” Journal
of Economic Literature, vol. XXXV (June 1997).
28 There is a fairly low correlation between wealth and income, which may largely be due to the fall in income that
typically follows retirement.
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households, he was able to estimate how much of the change in inequality each variable
accounted for between 1979 and 1996.29
Of the total increase in U.S. personal income inequality Burtless found that 28% was accounted
for by increased inequality in men’s earnings and 5% by increased inequality in women’s
earnings. The changing composition of households also played a role. Between 1979 and 1996
there was an increase in the correlation between husband and wife earnings, and that contributed
an estimated 13% to the overall increase in inequality. This is the result of a surge in women’s
employment and the general tendency of married couples to have similar educational
backgrounds and earnings potential. The increase in correlation resulted in a rise in the share of
income accruing to households in the upper income classes.
At the same time there was a decline in the percentage of husband-wife households. Income is
more unequally distributed among single adult households than it is among married-couple
households. Burtless estimated that this shift accounted for 21% of the increase in inequality
between 1979 and 1996. Thus, changes in the composition of households accounted for a third of
the overall increase in inequality.
Conclusions and Policy Considerations
Existing measures of income fall well short of the theoretical ideal that would indicate how well
off individuals or households are. Not all kinds of income are counted, and thus the distribution of
a household’s assets may affect one’s apparent position in the income distribution.
Taking the existing measures at face value, however, several observations can be made. First, the
distribution of income in the United States has become increasingly unequal since the late 1960s.
Second, the U.S. income distribution is more unequally distributed than is the case for a large
selection of other industrialized countries.
The distribution of earnings is more unequal than is the distribution of household income. Of
particular interest is that the gap in earnings between highly educated or skilled workers and less
skilled workers has grown substantially. Several explanations have been offered, but the one most
widely accepted is that technological advances in recent years have increased the demand for
more highly skilled labor relative to its supply. Policies that boosted the supply of skilled workers
would thus seem likely to narrow that gap and act as an equalizing influence on the income
distribution.
Given the large gap in pay between skilled and unskilled workers that has developed, it might
seem there is little need for additional incentives for prospective and current workers to continue
their education and training. Any additional incentive would likely pale in comparison to a
lifetime of higher earnings, assuming workers understand these relationships. That is one reason
some have advocated doing more to improve the education of the very young.

29 Gary Burtless, “Has Widening Inequality Promoted or Retarded US Growth?” Canadian Public Policy - Analyse de
Politiques, vol. xxix, supplement/numéro spécial 2003.
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In many cases there may be costs associated with policies designed to reduce income inequality.
Changes in tax rates, subsidies for the unemployed, or other transfers for low-income households
may also have undesirable effects in the labor market and discourage some from taking jobs.
Some of the greater income equality found in other countries, however, may be due to the fact
that existing transfers are more directly targeted at lower income households. Redirecting transfer
payments from middle to lower class households could increase equality in the distribution
without an increase in the amount of income being redistributed.

Author Contact Information

Brian W. Cashell

Specialist in Macroeconomic Policy
bcashell@crs.loc.gov, 7-7816

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