Two economists at the University of Michigan, Martha J. Bailey and Susan M. Dynarski, studied Census data and a longitudinal study to measure these trends among two cohorts of young people: those born in the early 1960s and those born around 1980. In their report, “Gains and Gaps: Changing Inequality in U.S. College Entry and Completion” (PDF here; abstract of related paper here), they found that the more recent cohort received more college education at all income levels. However, the gains were greatest at the top of the income distribution:
Those born to parents at the top half of the income distribution boosted their college entry rates by some 22 percentage points between the two periods. Those at the bottom quarter of the income distribution saw only a 10 percentage-point improvement. Rates of college completion showed a similar pattern: an increase of 18 percentage points for the top income quartile as compared with only 4 percentage points for the bottom quartile.
For the earlier group, rates of college completion for men and women were similar, but women in the later group had much higher rates of completion—especially those from a privileged background:
In college entry, persistence, and completion, women in the top-income quartile have pulled away from the rest of population. In the later cohort, an astounding 85 percent of women in the top quartile entered college. The gap between the top and bottom-income quartiles in college entry rose by fifteen percentage points among women. The comparable increase for men is seven percentage points. The pattern in completion is similar, with the gap between the top and bottom quartiles rising by seventeen percentage points among women and eleven percentage points among men.
The female advantage in college entry is not new; it has been a fact for every cohort of young women born since 1950, and the gap is now around 10 percent. Women gained the advantage in college completion (by age 25) with the cohort born in 1966, and the gap for this measure is also around 10 percent at present.
Economists and policy makers like to look for the causes behind trends, and these economists looked at two factors: high school graduation rates and cognitive skills. They note that they are unable to show actual causation; they can show only high correlations, acknowledging that (for example) unknown factors compelling students to drop out of high school may be the true causative factors for lower college completion rates.
When the economists compared the college achievements of those with high school diplomas and those with GED credentials, they found that increased high school completion rates explained only a small fraction of the increases in college entry and completion.
To measure differences in cognitive skills, they looked at students’ scores on the Armed Forces Qualification Test. They measured how well differences in these test scores could predict the gaps between the highest and lowest income quartiles in terms of college entry and completion. They found that cognitive skill differences explained less of the achievement gap for the later cohort than for the earlier cohort. In other words, for college achievement, brainpower seems to be diminishing in importance compared to economic privilege. That suggests that income inequality is causing our economy to lose badly needed talent.
But what about the increasing college achievement difference between men and women? The economists find the most convincing explanation is that college has increased the prospects for marriage and employment for women more than it has for men, and women are responding to these motivations by getting more college education. As the cost of a college education keeps rising, it seems likely that women from more-privileged backgrounds will have increasing ability to act on these motivations compared to less-privileged women.