Is early marriage about to become the norm once again in American life? If so, Ann Landers is the first to spotlight the trend. On Aug. 19 she ran a letter from 22-year-old "Manhattan Mary," who has a job in "the advertising field." "My steady friend," Mary says, "is stable, solid and dull. He wants to marry me. Frankly this AIDS thing has me scared to death. I'm considering saying yes and getting out of the rat race. I know he's healthy, and I'm scared to date anyone else." Awareness of AIDS is unusually high in Manhattan and in an arts-related business like advertising. But the disease is spreading and taking more victims, and Manhattan Mary's fears are likely to be more common.

Should she sail into this safe but dull harbor of marriage? Landers is skeptical: "Marriage, even to Mr. Dullsville, is no guarantee of fidelity, and therefore no guarantee that he'll never bring home AIDS. Put everything on hold," she says. It's a reply in line with the progressive tone of the day -- we shouldn't get more concerned about this disease than is statistically warranted, lest we encourage others to shun or mistreat members of the groups most likely to be infected -- as well as with the romantic idea of holding out for Mr. Right. Yet I have the hunch that Manhattan Mary and others like her are not going to take Landers' advice -- and that Landers herself may change her mind over the next few years.

Some recent statistics suggest that early marriage is suddenly becoming the American norm again. The Census' household formation statistics tell the story. In the 1970s the number of single households -- those headed by an unmarried, separated, divorced or widowed person -- rose by 78 percent, five times the rate at which the number of married households increased. The age at which Americans first married in these years rose to the highest levels since the early 20th century, when men typically had to postpone marriage until they could afford to support a family and many more men and women than today remained single their whole lives. With rising affluence, however, Americans were free to marry earlier, and in the years of unparalleled economic growth after World War II marriage ages were the lowest in our history: most American women married before they turned 21.

Starting around 1962, the trend reversed: with affluence still increasing, combined with widely available birth control and attitudes favorable to sexual liberation, Americans were free to postpone marriage until they were in their late thirties. It became standard practice for young Americans after they had finished school to set up their own households and live as single people for several years. Garden apartments sprang up all over the country, Club Meds and singles resorts burgeoned from the Caribbean to Maine. Young singles became the fastest growing demographic category in America.

Now, suddenly, that is no longer the case. In 1986 the number of single households increased barely at all. The number of marriages rose. The percentage of new households formed by married couples rose from 12 percent in 1983-84 and 19 percent in 1984-85 to 35 percent in 1985-86 and 60 percent in 1986-87. During the early 1980s, the number of young people living with their parents started to rise, apparently because of the recession. But in the sixth year of economic recovery, the trend continues. The 1970s pattern of a long period of singles existence now seems to be changing. Young Americans are staying home longer and marrying earlier. Welcome back to the 1950s.

AIDS is surely not the only reason for this change. Low entry-level wages combined with rapidly rising housing costs persuaded many young singles to stay home. And the years since the late 1970s have been an age of restraint, with less divorce and abortion, less alcohol drinking and drug use, a more moderate diet and more restraint in sexual behavior.

Then the threat of AIDS appeared. Evidently it is convincing millions of young Americans of something traditional morality has always argued: you're better off in the confines of a safe and early marriage. My forecast for the 1990s is thus for earlier marriage and higher birth rates. There may be as well some decline in the percentage of working women, though not much: most Americans want the affluence they can achieve only with two paychecks. The same attitude, however, should work against divorce, which is ruinous economically, especially to women.

This is, I think, mostly good news. Married people are economically more productive and culturally more stable than singles, and a higher birthrate will produce the larger number of young Americans we need to provide a well-educated work force for tomorrow and to pay for us baby boomers' Social Security benefits. Of course, some people will remain unhappy; Manhattan Mary may be miserable with Mr. Dullsville. But the liberation era has taught us that nothing can guarantee us happiness, and we may be concluding, as people did in the 1950s, that we're better off marrying young and having more kids.

The writer is a member of the editorial page staff.