Average income of families in the top quintile of the family income distribution, divided by the average income of families in the bottom quintile.
Ratios are calculated by the Stanford Center on Poverty and Inequality, using the U.S. Census Bureau Historical Income Tables for Families. The Census Bureau’s estimates are based on data from the Current Population Survey Annual Social and Economic Supplement.
The Current Population Survey defines a family as a group of two people or more (one of whom is the householder) related by birth, marriage, or adoption and residing together; all such people (including related subfamily members) are considered as members of one family. Beginning with the 1980 Current Population Survey, unrelated subfamilies (referred to in the past as secondary families) are no longer included in the count of families, nor are the members of unrelated subfamilies included in the count of family members.
In the Annual Social and Economic Supplement, respondents report income from the previous calendar year, but they report family and household composition as of the date of the survey. The measure of family income used by the Census Bureau is the sum of the income obtained by all family members 15 years old and over. Income refers to the amount of money income received from each of the following sources: earnings; unemployment compensation; workers’ compensation; social security; supplemental security income; public assistance; veterans’ payments; survivor benefits; disability benefits; pension or retirement income; interest; dividends; rents, royalties, and estates and trusts; educational assistance; alimony; child support; financial assistance from outside of the household; and other income.