W.D. Kiernan, rightly smelling a fault: "That's not even keeping up with population growth" My mistake, I was reading the wrong column completely. Percentage of the population aged 18-24 attending college rises, pretty evenly, from 25 per cent to 38.9 per cent, between 1967 and 2005. Column F in this excel table http://www.census.gov/population/socdemo/school/TableA-5a.xls