The nonpartisan Congressional Budget Office recently released a much-discussed study showing that over the past three decades the income of the highest-paid Americans has soared while the income of others has grown much more modestly. Here’s a rundown of some statistics illustrating the growing income gap.

But first, some context. These numbers reflect income, not wealth. So a retiree who owns two houses and three cars may be far better off than someone with a higher annual income, two kids in college and a mortgage. It's worth noting that income includes investment income and capital gains.

Also, although a 2010 Organization for Economic Cooperation and Development study suggests that there is less income mobility [PDF] in the United States than in many other developed countries, someone in the richest 1 percent this year may have been in an entirely different category 30 years ago. Take Bill Gates. In 1979, Gates was 24, and Microsoft hadn’t even incorporated. He was likely in the bottom tier of earners. More recently, of course, he has easily been in the top 1 percent. According to a 2007 Treasury Department study [PDF], “roughly half of taxpayers who began in the bottom income quintile in 1996 moved up to a higher income group by 2005.”

Third, though income growth has been unequally distributed, real income for all groups has grown over the past three decades.

In spite of those caveats, the gap between richest and poorest is far greater than it used to be. All income numbers have been adjusted for inflation, and all household income data are adjusted for differences in household size [PDF; see Appendix A]. Please note that different subsections take different years as a baseline.

(Update, 11/4) You can also find out how income inequality in your county ranks compared to other parts of the U.S. using this interactive chart.

Overall income growth for the country as a whole

Disposable personal income per capita:

1980 $18,822 1990 $23,542 2000 $28,911 2010 $33,125

All figures in constant 2005 dollars. Source: Census.gov



Unevenly distributed growth

Top 1% of Households 275% Poorest Fifth of Households 18.3% Middle Fifth of Households 35.2%

Source: Congressional Budget Office

1979 2007 Top 1% of Households 10.5% 21.3% Poorest Fifth of Households 2.9% 2.5% Middle Three Fifths of Households 47.8% 38.5%

Source: Congressional Budget Office

Large gains for the highest earners, modest gains for the rest

1980 1990 2000 2007 Top 1% of Households $339,200 $586,000 $1,038,700 $1,319,700 Poorest Fifth of Households $14,800 $14,800 $16,500 $17,700 Middle Fifth of Households $42,600 $45,000 $50,400 $55,300

All figures in constant 2007 dollars. Source: Congressional Budget Office



Decline in median individual income for men, slight gains for women throughout the 2000s

1995 2000 2005 2010 Men $32,051 $35,885 $34,929 $32,137 Women $17,232 $20,338 $20,747 $20,831

All figures in constant 2010 dollars. Source: Census.gov

Comparison to other countries

Income inequality on a scale from 0 to 1, 1 being the most unequal:

France 0.239 Poland 0.305 Greece 0.307 United States 0.378 Mexico 0.476

Source: Bertelsmann Stiftung