1970s: The birth control pill abets the "sexual revolution," leading to widespread change in sexual mores.

1990s: The sexual revolution is curtailed by the spread of incurable sexually transmitted diseases, including herpes and AIDS.

1970s: A numerical decline in the number of two-parent families in the U.S. begins in this decade. The decrease continues at a rate of about 4

1990s: The decline in the number of two-parent families stabilizes in mid-decade and slowly begins to reverse. there are about 25.1 million married couples with children in the U.S. in 1995— an increase of about 521,000 since 1990.

1970s: Teenagers and young adults become a distinct demographic with enormous buying power and hence, the power to influence popular culture. The choices, beliefs, and icons of a youthful generation are seen as significant historically.

1990s: Economists note that people born in the post-World-War-II years who...