WASHINGTON (CBS DC) — The growing diversity of the U.S. population is not being reflected in America’s college campuses.

A recent study from professor Peter Hinrichs of Georgetown University finds that while desegregation has led to massive changes on college campuses since the 1960s, diversity has actually slowed down in the decades since then.

“There’s basically less segregation over time, but it was falling faster in the late ’60s and early ’70s,” Hinrichs, an assistant professor of public policy, told The Huffington Post. “Now it’s a little bit closer to the case of perfect integration, but still not anywhere near that,” he said.

The study focuses on black and white students, not those in other racial and ethnic groups, and he examines “exposure” and “dissimilarity” of black and white students as two measures of desegregation. Hinrichs uses federal data from every college, filed since the era in which desegregation started in the 1960s.

The study used a two-pronged method of analysis to derive its diversity data.

The first is “exposure,” which is the percentage of black students at colleges attended by white students, and vice versa. Hinrichs shows that from 1968, the typical white student attended a college that was 2.3 percent black. But by 2009, the typical white student attended a college that was 9.8 percent black. This percentage gain is much larger than overall black enrollment during this period, which also rose, from 5.5 percent to 13.7 percent.

The second method of analysis is that of “dissimilarity,” which examines the extent — on a scale of 1 to 100 — to which black and white students attend similar institutions. So if every college in the country had 10 percent black students and 60 percent white students, the index would be 0 because the black and white enrollment patterns would be identical.

Hinrichs found that the index fell sharply in the direction of desegregation as the civil rights movement and court rulings led predominantly white colleges to recruit black students. In 1968 the index was 63.9 percent, and by 1972, the index had dropped to 52.5 percent. But since then, movement has been modest. and the figure had dropped only to 48.0 percent by 2009.

In an interview with Inside Higher Ed, Hinrichs said that it is hard to say what the index should be in a desegregated society. He noted that elementary and secondary schools have a higher index. Further, he said that most students (of all races) attend colleges and universities near where they live. Since the black population is not evenly distributed in the United States, there are likely to be regions where colleges have relatively low black enrollments.