Few ideas are so deeply embedded in popular consciousness and political debate as what I'll call the "two-earner myth." It holds that two workers -- a husband and a wife -- are now needed to to make the same income that one worker -- the husband -- attained in the 1950s and 1960s. Women have flooded into the labor market (the theory holds) mostly to offset the lost earnings of their husbands. Her income gets the couple back to where it would have been if his wages weren't dropping. Families feel stressed. And why not? Mothers must choose between putting food on the table and caring for their children.

The theory has broad appeal. Conservatives see it as one reason that "traditional" families are under assault; liberals view it as a pretext for aggressive government programs to raise economic growth. But the theory is mostly bogus, though not the feelings that go with it (as I will explain in a moment). Here's what actually has happened:

* Women didn't initially enter the job market to make up losses in their husbands' salaries. The influx began in the 1950s, two decades before any slowdown in men's wages. Between 1950 and 1970 the proportion of wives with paid jobs rose from 23 percent to 39 percent. By 1995 it was 61 percent. Maybe the pioneer working wives of the 1950s and 1960s sought to raise their families' incomes; if so, the reason wasn't their husbands' falling wages. Most wages rose rapidly during these decades.

* Since the early 1970s, men's wage growth has slowed. But the increase in the number of wives with jobs is concentrated among upper-in\come couples -- precisely those who need the extra money least. Among the richest fifth of husbands, the share of working wives rose from 45 percent to 71 percent between 1973 and 1993, reports economist Gary Burtless of the Brookings Institution. Wealthier husbands not only earn more but their wages and salaries have shown the best gains. By contrast, wages for many low-skilled workers have dropped (after adjusting for inflation).

* The "real" incomes of most two-earner couples have consistently risen. Among poorer workers, wives' earnings may offset some drop in their husbands' wages; but that isn't true at the top of the income spectrum or probably in the middle. In 1995 the median two-earner couple -- the one in the middle of the income distribution -- made $55,823, about 23 percent more in "real" dollars than a similar couple in 1970, says the Census Bureau. (Actual gains in purchasing power are even higher because the consumer price index, used to estimate real incomes, overstates inflation; therefore, it understates income.)

If men's wages suddenly surged, some wives might stampede back into the kitchen. Most would not. We've had an upheaval in attitudes and customs. Call it feminism, call it ambition, call it anything. Most women -- and most men, too -- now think that women should have the chance to work and pursue a career. In 1945 that wasn't true. As a society, we've created more social choices. In general, this is progress. It gives people more freedom to live as they see fit. But the new choices have spawned new anxieties, complaints and consequences.

One surprise is more economic inequality: a point made by Diana Furchtgott-Roth of the American Enterprise Institute as well as Burtless. Well-paid workers increasingly marry each other and dominate the top of the income spectrum, while poorly paid workers increasingly don't marry (or don't have two workers) and drift toward the bottom. Between 1970 and 1995, the share of families with only a single mother rose from 11 percent to 18 percent. Since the late 1970s, these changes may explain about half of the increase in family income inequality, estimate Burtless and economist Lynn Karoly of the Rand Corp.

Another unintended consequence is that families do increasingly need two earners for a middle-class lifestyle, while only one was required for the 1950s' or 1960s' version. But here's the catch: today's middle-class lifestyle is a lot richer. If people want to duplicate their parents' lifestyles, they can unplug their air-con\ditioners, sell one of their cars, discard their VCRs and PCs and stop sending all their kids to college. As more wives work, the two-earner couple becomes the norm. Couples still can have one partner stay at home, but only if they don't mind sliding down the income ladder or are exceptionally rich.

Let me give a simple example to show why. Suppose we have two sets of identical twins: Pete and Joe; and Mary and Sally. They marry. Pete weds Mary, and Sally takes Joe. They all have jobs, and each earns $35,000 a year. Each also gets a 10 percent increase every year. (I'm simply assuming away falling wages or inequality.) After five years, everyone earns almost $56,400; each couple's income is nearly $113,000. They buy identical houses and cars; they vacation together. They have the same lifestyles. Now Mary and Sally have babies -- and Sally quits her job, while Mary (after maternity leave) goes back to work.

Watch what happens. Sally and Joe's income falls to 50 percent of Pete and Mary's. It doesn't make any difference that Joe still makes a good salary and that it's increasing 10 percent a year. Suddenly, their lifestyles are no longer the same. Sally and Joe have trouble paying bills. Maybe they move to a smaller home; maybe they can't afford a new car or a vacation. Meanwhile, Pete and Mary, though comfortable financially, feel guilty about not spending more time with their baby. There's more tension as they try to juggle their schedules. And everyone wonders how Mom and Dad could have done it all while Mom stayed at home.

One reason is that Mom and Dad didn't live so well, materially at least. Another reason is that Mom didn't have much choice -- and may occasionally have yearned to do something aside from making the bed, checking the homework and cooking dinner. The larger point is that the dilemmas of the two-earner couple don't arise mainly because incomes (men's or otherwise) are growing slowly. People compare themselves to people like themselves. As more women work, the comparisons adjust quietly. It's women's wages, more than men's, that create pressures for women to work. We have more choices now than ever, but they aren't necessarily easier.