Despite decades of integration efforts, racial preference is still seeping into the classroom. Now, a new study, done using economic principles, suggests that the extent to which teens form racially exclusive bonds depends largely on just that — their race.

But it’s not as simple as preference. Young people, especially African-Americans, are also more likely to be exposed to those in their own ethnic communities, making segregated school communities all the more inevitable.

A team of Stanford economists, led by Matthew Jackson, used data from the National Longitudinal Study of Adolescent Health (Add Health), which collected information from students in grades seven through 12 at 84 schools across the country.

In examining data on nationwide friendship networks, the Stanford team determined that students in particular tended to form friendships based on common ethnicity to a greater extent than individuals in the general population did. Their findings were published in the Proceedings of the National Academy of Science.

Racial self-segregation is part of a phenomenon called “homophily,” the tendency of individuals to bond with those who share similar characteristics. In this case, the team determined that the selective bonding has two sources: Students can be biased in whom they befriend, or might be bound by inherent bias in the opportunities they have to meet people in different ethnic communities.

Of course, polling students on racial sentiments, or simply observing their friendship groupings, isn’t an accurate way to determine how ethnicity affects relationships. So the team used a well-known economic method, called revealed preference theory, which examines individual preferences within the context of opportunities. Read more at AOL.news