INFLATION, the popular theory goes, is driving housewives into the labor force. Sure, some mothers are working now because they want to, because they want the satisfaction of a career, but a lot of housewives are working simply to help the family make ends meet. The second income, once a luxury in a family, has become a necessity because of inflation the theory goes.

In the old days, the days before inflation, middle-income families, with only the father working, could still afford a second car. These families could send their children to college on the father's income, and could move into a four-bedroom house on his income. But that was before inflation. Now, according to the popular analysis, the middle class can't keep its head above water with a middle-class income and that, more than any other factor, is driving the housewives into the paid labor force.

We know from the Labor Department that the number of women working has increased by 12 million to a total of 41 million in the past 10 years, which means that more than 50 percent of American women worked last year. The Labor Department doesn't know why the increase has been so dramatic. The last time it surveyed women on the question was in 1963 and a lot has changed since then. So, in the absence of facts, the simple theory that women are working to keep their families ahead of inflation has emerged. "It's something people automatically say," says economist Barbara Bergman. She says you read it every day in the popular press and she has even seen it in a banking newsletter. "I don't believe it's correct." Bergman, who was trained as an economist at Harvard and later taught there, now is a full professor of economics at the University of Maryland. She and feminist Sheila Tobias have developed a quite different analysis of why women are working and if they are right, inflation is getting a bum rap. What's more important, we are not understanding what is behind one of the most significant social and economic changes of out times.

"The basic idea," says Bergman, "is that women who decided to withdraw from the labor force used to have a lifelong commitment to be supported in a style and with a status that was in accordance with their husband's style and status. Obviously, the increase in divorce has made this a very poor presumption. A woman who depends on it is not really in a good situation.

"To be a housewife is a very risky occupation. It's riskier than working with the steel structure on a skyscraper. That's considered a dangerous occupation, but in terms of accidents it's not quite as risky as being a housewife. A third of them don't fall off, [but about that many] housewives essentially lose their economic base by being separated from their husbands.

"Many of them have the illusion that they will continue to be supported by their husbands, but the facts show that in 80 percent of these cases or thereabouts the support payments are either delinquent or they don't come at all.

"It's also a matter of status. If you are the wife of a lawyer or a doctor you have the status of a wife of a lawyer or a doctor. When he leaves, you may become a checkout person at the drug store.

"So, given the divorce statistics, I think a lot of younger women are seeing that putting all or even many of their eggs in the basket of commitment to staying home is a dangerous game. In my view, that is one of the things that is causing more and more women to enter the labor market. We're getting to the point now, where fewer women are leaving jobs even temporatily to raise children.

"The institutions which made being a housewife a reasonable career for many women aren't there.You might say the occupational hazards have increased.

"Now, after this inflation business, you have to remember that real incomes have been going up. This is after accounting for inflation. In the post-war period, there has been something like a 2 1/2 percent increase in real income a year. Just on the basis of the husbands' salaries, the provisions for the families have not been damaged by inflation. This myth that somehow inflation is eroding the economic basis of the family, based on the husband's salary, is completely false.

"Another reason for women going into the marketplace is that this 2 1/2 percent increase in real income has been accruing to women as well as to men. Women's salaries have been increasing, too. They've stayed about 40 percent behind men's salaries, but they are keeping up. They're not falling [further] behind. So, women have a choice. You can stay home and do housework or you can go out and earn money. The real money women are earning has been increasing. This is an incentive to choose this route."

There are, in other words, poweful and complicated forces pushing mothers and wives out of the homes and into the work force. Inflation may have something to do with it and higher material expectations that can be attained with two incomes may also have something to do with it. But what Bergman is saying is that young women now are looking around them and seeing the plight of the millions of displaced homemakers who devoted the career years of their lives to making a home for their husbands and children and who, in the end, found themselves holding a divorce decree, getting some alimony -- if they were lucky -- and having no skills with which to support themselves. Young women are seeing this happen to their own mothers and to the mothers of their friends and they are saying to themselves that it's not going to happen to them. They're not going to work to keep their families ahead of inflation, says Bergman. They're going to work, at least in part for self-preservation.