Year Bachelor’s degree Post-graduate degree
1960 2.5 2.6
1970 4.0 5.0
1980 7.0 8.7
1990 11.5 8.8
2000 13.7 10.3
2010 15.9 11.1
2013 16.4 11.9
2014 16.6 12.0

Source: Pew Research Center tabulations of 1960-2000 decennial censuses and 2010, 2013 and 2014 American Community Surveys (IPUMS)