About 90% of the U.S. population has graduated high school, a dramatic improvement in educational attainment that began when compulsory education was adopted by every state a century ago.

But the most striking social shift is the shrinking of the high school attainment gap between Blacks and the national average.

In 1940, when the U.S. Census Bureau started asking about educational attainment, only 7% of Blacks had a high school education, compared with 24% for the nation as a whole.

In recent years, Black educational attainment has been much closer to the national average and today, 88% of Blacks or African Americans have a high school diploma, just shy of the national average, according to census data released last month from the Current Population Survey.

This analysis of educational data does not include people who categorize themselves as Black in combination with another race. It focuses on those who identify themselves as “Black alone.”

Universal compulsory education is a major reason for skyrocketing high school attainment but demographic momentum also plays a role. As older and less educated generations are replaced by more educated youth, the nation’s educational attainment rises.

College attainment has also increased, though not as dramatically, and the progress of the Black population has been considerable in the context of rising college education overall.

In 1940, less than 5% of all adults and only 1% of Blacks had completed four years of college. The persistent gap in rates between Blacks and the national average was 4 percentage points at that time, while Black college completion was one-fourth the national rate.

In 2019, both groups had much higher college attainment rates overall, with the national average at 36%, while 26% of Blacks ages 25 and older had attained a bachelor’s degree. Despite the percentage point gap, Black college completion has grown closer to about three-quarters of the national average.

Educational attainment among younger adults ages 25 to 39, which provides a glimpse of future trends, is higher compared with older adults ages 70 and older for both the national average and Black adults.

Black and average high school attainment for ages below 55 are on par.

The education success story continues for young adults. In the last 50 years, both the Black and national average high school dropout rates declined rapidly and college enrollment increased steadily.

The once significant difference in the high school dropout rate between the Black population and national average is no longer.

The national average dropout rate declined from 19% in 1968 to about 6% in 2018. The Black dropout rate fell more steeply from 33% to 5%, bringing it in line with the national average.

At the college level, the significant enrollment gap between the Black population and national average still exists but has narrowed considerably.

Average enrollment for young adults increased from 26% to 41%. At the same time, the proportion of Black young adults in college more than doubled, rising from 15% to 38%.

(Jennifer Cheeseman Day is a demographer in the Census Bureau’s Communication Directorate.)