美国收入不平等的演变、其后果及一些政策措施

byTanweer AkramIndependent ScholarandKhawaja MamunLongwood UniversityMarch2026 LevyEconomics Institute of Bard College, founded in 1986, is a nonprofit, nonpartisan,independently funded research organization devoted to public service. Through scholarship andeconomic research, it generates viable, effective public policy responsesto important economic Levy Economics InstituteP.O. Box 5000Annandale-on-Hudson, NY 12504-5000http://www.levyinstitute.orgCopyright © Levy Economics Institute 2026All rights reservedISSN 1547-366X ABSTRACT This paper discussesthekey concepts and main stylized factsconcerning household real incomeandincome inequality in the United States in recent decades.It explains the widely usedsummarymeasures of incomedistribution,which reveal that income inequality in theUShas KEYWORDS:Household Real Income;Income Inequality;Macroeconomicand Social Effectsof Inequality;UniversalBasic Income;Job Guarantee JEL CLASSIFICATIONS:D10;D31;D63;E02;E64 SECTION I: INTRODUCTION In the United States, rich households have become richer, while lower-income householdshavenot gained much since the 1970s(Horowitz, Igielnik, and Arditi2020). Indeed,based onallwidely used metrics of incomedistribution,it is unequivocal that incomeinequality hasworsened.There are many reasons for thiswidening;the increase cannot and shouldnot be The paper is structured as follows. Section II describes the key stylized facts concerning thedistribution of income in the United States in the past several decades. Section III presents fourkey summary measures of income inequality. Section IV brieflyaddresses the cause of rising SECTION II: THE STYLIZED FACTS CONCERNING INCOME DISTRIBUTION The income inequality discussed in the paper is that of pre-tax household real income, asreported by the USCensus Bureau.It is based on data about the amount of money incomereceived, outside of capital gains, by householdsfrom the following sources: earnings;unemployment compensation;workers’ compensation;SocialSecurity;supplementalsecurity inequalitydoes not reflect non-cash benefits, such as food stamps and Medicare.Income andearningsover time are adjusted for the cost of living using an appropriateconsumer price index A clear and distinct manner of illustrating the marked rise ofincome inequality is to compare theevolutionsof the mean and median family real income over time, as shown in figure 1,below.Figure 1 showsthatnot onlyhasfamily mean and median income risenover time,but the gapbetween mean and median incomes haswidenedboth in absolute and relative terms.Meanrealincome has risen from$41,000in 1950 to$145,000in2024 (measured in constant dollars). Table 1,below,displays the evolution of householdmedianreal income andhouseholdincomeofquintile groupsat the beginning of each decadefrom 1970 to 2025.It also gives the share ofhousehold income by quintiles and two summary measuresof incomeinequality. While medianrealincome has risen during this period, the datarevealanotableriseinincome inequalityin theUnited States. The sharesofincome going tothe lowestthroughthefourth income quintile SECTION III: SUMMARY MEASURES OFINCOMEINEQUALITY Summary measures are useful in understanding the evolution of incomedistribution.Atkinson(1983), Cowell (2011), and Sen (1992,1997) coverin richly textured detailsthe economicsas The four key summary measuresofincomeinequalitythat are discussed hereare theGini indexof income inequality, the mean log deviation of income(MLD), theTheil index of income AGini index of0expressesperfect equality, where everyone has the same income, whileaGiniindex of 1 expressesmaximalinequality, where only one person has allthe income. Another way incomeforthe population.It is convenient to view the Gini index in terms of the Lorenz curve,where the percentage of the populationis represented on the horizontal axis andarrangedfrom The MLD is another measure of income inequality. The MLD is 0 wheneveryone has the sameincomeand takesalarger positive value as income becomesmore unequal, particularly at the The Theil(1967)index is another measure of income inequality, drawn from information theory.It is particularly useful for decomposing inequality intoitscomponents. If everyone has the sameincome,then theTheilindex equals0. However, if one person has all the income,then theTheilindex givesthe result ln(N), whereN is the number of individuals and ln(.) is a natural logarithm. The Atkinson index of inequality illuminateswhich end of the distribution contributed most tothe observedincomeinequality(Atkinson 1970, 1983; Atkinson and Bourguignon2000).Adistinct advantage of the Atkinsonindexisthat itconvertedinto anormativemeasure byimposing aparameter,e,toweighincome. Theeparameter reflectsthe evaluator’s inequalityaversion,since it quantifies the social utility that isobtainedfromacomplete redistribution of SECTION IV: THECAUSES OF RISING INCOME INEQUALITY There is no single cause that explains rising income inequality in the U