Income Inequality in the United States: Decomposing the Gini Coefficient

This paper uses March CPS data to decompose the Gini coefficient by source of income. The sources of income, divided by labor income, capital income, and public transfer income, include earnings; interest, dividends, and net rentals; public assistance and welfare; retirement funds; self-employment; farm or non incorporated self-employment; nonfarm self-employment; Social Security or railroad retirement; supplemental security; wages and salaries; and unearned sources. The decomposition yields the share of a source in total income, the source Gini corresponding to the distribution of income from a source, the Gini correlation of income from a source with the distribution of total income, and the impact of a marginal change in a source on overall income inequality. Labor income had the largest negative impact on income inequality (resulting from wages and salaries mostly), while capital income did worsen it but on a much smaller scale. Public transfers that favor bottom income groups helped to alleviate income inequality for both individuals and households.