When the Census Bureau rounded up the usual statistics, it recorded another step in the movement of women into the work force. The figures released in their special report on women show that in 1950 less than one-third of adult females were employed outside their homes, and by 1980 more than half were.

In response to this familiar phenomenon, we were offered a familiar explanation. "One reason," said a researcher, "is that there is less work to do at home."

By now the notion that there is less work to do at home has become the accepted wisdom of modern America. It is an article of faith that the wonders of modern technology have freed women from the household burdens of their foremothers.

After all, women don't make candles, soap and cloth at home anymore. We have stoves and washing machines and even vacuum cleaners. With machines doing the housework--so the theory goes--women could, perhaps had to, go outside the house to work.

What this theory does is to simultaneously knock the amount of household labor done by both the average housewife and the average employed wife. But this favorite theory just doesn't hold up to rigorous analysis.

The real effects of household technology on women's lives have been much more ambiguous than we generally believe. Modern tools may have eliminated drudgery--we don't wash our clothes by the river with stones anymore--but they do not seem to have reduced the amount of labor women actually perform.

Ruth Cowan, a professor at the State University of New York at Stony Brook, makes this point in her new history of household technology with the give-away title, "More Work for Mother." At the beginning of American history, she shows, most chores of daily life were shared by men and women. To make a meal, men chopped the wood, women cooked the stew. One by one, men's tasks were industrialized outside the home, while women's stayed inside. Men stopped chopping wood, but women kept cooking.

Homemaking technology raised our level of comfort and standard of living, but didn't lower the amount of women's work. The stove, which replaced the open hearth, made cooking easier in one way and more complicated in another. At the same time, the three-part meal replaced the one-pot meal. Today, with or without a microwave oven, frozen and occasional fast food, the average woman spends 21 hours a week on meals, once you include shopping, cooking, serving and cleaning up.

As for laundry, our ancestors generally had fewer clothes and/or more help keeping them clean. Laundry was one of the few housekeeping chores that had been industrialized in the 19th and 20th centuries. For a time, commercial laundries picked up and delivered the wash to most middle-class households.

The advent of the washing machine during World War II meant, says Cowan, that "the woman endowed with a Bendix would have found it easier to do her laundry but, simultaneously, would have done more laundry and more of it herself than either her mother or her grandmother had."

Technology has increased the productivity of the average housekeeper. The good news is that by 1950 a housewife could do what it took a staff of three or four to do in 1850. The bad news is that she did it alone.

It also changed the nature of housework. As Cowan writes, "Before industrialization, women fed, clothed and nursed their families by preparing . . . food, clothing and medication. In the post-industrial age, women feed, clothe and nurse their families . . . by cooking, cleaning, driving, shopping and waiting. The nature of the work has changed, but the goal is still there and so is the necessity for time-consuming labor."

It is just not true that American women entered the job market because they had time on their hands. Even today housewives spend 50 hours a week on work related to homes and family, and employed wives spend 35 hours a week. Both still do housework virtually alone.

But it is true that technology has allowed mothers--who go to the marketplace for one reason or another--to do so without damaging their families in crucial ways. The family of today's working mother, unlike that of half a century ago, doesn't have dirty clothes and cold meals. But it probably has a weary mother.

If all this makes you skeptical about the value of "labor-saving" devices, good. Machinery may glut the market, but the commodity most in demand is in short supply. It's that precious thing called human help.