Mean Family Income By Quintiles

See Historical Income Tables: Families from the Census Bureau. They also have a link for Gini coefficients for family income going back to 1947. See also Historical Income Tables: Households.

First I have the mean income, in 2015 dollars, for each quintile and the top 5%, averaged over 5 decades, with the first being 1966-1975. Then a timeline chart. The mean income for the bottom quintile jumped from 16,128 in 2014 to 17,367 in 2015, a gain of about 7.7%. For households it was 6.6%.

Year	Lowest	Second	Third	Fourth	Highest	Top 5%
1966-1975	16,809	36,623	53,203	72,024	123,526	187,749
1976-1985	17,147	37,826	57,476	80,451	137,761	199,813
1986-1995	16,788	39,422	61,539	89,229	169,149	272,936
1996-2005	18,232	42,706	67,864	100,529	207,730	362,511
2006-2015	16,929	41,266	66,968	101,714	212,642	366,012