This publication takes an empirical look at four dimensions of the changing 20s. First, what the author regard as revolutionary shifts in the balance between young men and young women in education, employment, and earnings. Second, rapid changes in patterns of marriage and cohabitation. Third, changes in relations between 20-somethings and their parents regarding living arrangements and healthcare. And, finally, a startling shift in the definition of adulthood itself. The section on marriage and cohabitation focuses on the years 1970, 1980, 1990, and 2000. The report includes 23 charts and graphs including 11 related to marriage and cohabitation. (Author abstract modified)