The gap between rich and poor narrowed after World War II as unions negotiated better pay and benefits and as the government enacted a minimum wage and other policies to help the poor and middle class.
The top 1 percent’s share of income bottomed out at 7.7 percent in 1973 and has risen steadily since the early 1980s, according to the analysis.
Economists point to several reasons for widening income inequality. In some industries, U.S. workers now compete with low-wage labor in China and other developing countries. Clerical and call-center jobs have been outsourced to countries such as India and the Philippines.
Increasingly, technology is replacing workers in performing routine tasks. And union power has dwindled. The percentage of American workers represented by unions has dropped from 23.3 percent in 1983 to 12.5 percent last year, according to the Labor Department.
The changes have reduced costs for many employers. That is one reason corporate profits hit a record this year as a share of U.S. economic output, even though economic growth is sluggish and unemployment remains at a high 7.2 percent.
America’s top earners tend to be highly paid executives or entrepreneurs — the “working rich” — instead of elites who enjoy lives of leisure on inherited wealth, Saez wrote in a report that accompanied the new analysis.
Still, he added: “We need to decide as a society whether this increase in income inequality is efficient and acceptable.”