In 1999–2000, where undergraduates were enrolled and how much time they spent in the classroom was related to their age and life circumstances. Older undergraduates, who are more likely to have family and work responsibilities, were concentrated in public 2-year colleges (often called "community colleges") and they were very likely to attend on a part-time basis. Younger undergraduates were more likely to be enrolled in 4-year institutions and to attend full time. For example, 56 percent of undergraduates in their thirties and 63 percent of those 40 or older attended community colleges, while 55 percent of those ages 19 to 23 were enrolled in 4-year institutions. Moreover, 57 percent of undergraduates in their thirties and 70 percent of those 40 or older attended exclusively part time, while 63 percent of those ages 19 to 23 attended exclusively full time.

While women attended postsecondary education in greater numbers than men, no overall differences by gender were detected in the level of institution attended or in part-time or full-time attendance status. For example, 45 percent of women and 46 percent of men attended 4-year institutions (public and private not-for-profit institutions combined).⁵ Across all postsecondary institutions, 50 percent of men and 49 percent of women attended exclusively full time.

Some differences in patterns of enrollment at different types of institutions were found relative to racial/ethnic groups. For example, 39 percent of Black undergraduates attended 4-year institutions, compared with 48 percent of White students.⁶ Black and Hispanic undergraduates were more likely than White undergraduates to attend private for-profit institutions, though the proportions were relatively small (8 percent of Black and 9 percent of Hispanic students, compared with 4 percent of White students).

Where undergraduates enrolled differed by income level. Among dependent undergraduates,⁷ for example, the rate of attending 4-year institutions rose with each successive level of family income. The opposite pattern occurred for public 2-year institutions: as family income levels rose, the rate of dependent undergraduates who attended public 2-year institutions declined.