Bryan Lee, a senior at the University of California, Irvine, has noticed that some of his classmates adamantly declare their multiracial heritage while others choose not to identify themselves as being any particular ethnicity. The half-Korean, half-White biomedical engineering major is co-president of the university's Mixed Students Organization and says many of the group's members "absolutely refuse to check any box when they're filling out forms that ask one to describe his/her race." Lee himself has occasionally checked the "other" box in the list of racial identifiers. It's an exercise in choice that is driving a gradual but steady uptick in the "race unknown" category of enrollment stats at some colleges and universities. The shift results, in part, from a continuing rise in the number of interracial couples and the children born to those unions. But observers say it also hints at efforts by some current college students to be less fixated on skin color. For a small but growing number of multiracial students, freedom means being able to identify multiple ethnicities, or none at all.