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Casey B. Mulligan is an economics professor at the University of Chicago.

I noted several months ago that, for the first time in recorded history, women’s payroll employment might surpass men’s during this recession. This July women held 49.9 percent of all payroll jobs, and some recent research by Federal Reserve economists gives a sense of whether the current trend — heading toward a female-majority work force — will continue.

Obviously, millions of jobs have been lost during this recession. These job losses have been especially concentrated in industries like manufacturing and construction, which disproportionately employ men. The sharp contraction in these male-dominated sectors is part of the reason that male employment has fallen much more than female employment during this recession, and that women, as a result, have increased their share of the work force.

But with only the 49.9 percent figure, we do not know whether the high unemployment rate for men comes just because men are more likely to be laid off, or if it’s also because men are finding new jobs more slowly than women are.

Aysegul Sahin and Joseph Song at the Federal Reserve Bank of New York and Bart Hobijn at the Federal Reserve Bank of San Francisco have examined job flows data that help assess the relative importance of these various explanations for our “mancession.” And indeed, the Fed researchers found that the main reason for the “mancession” is that so many more men than women lost their jobs — and not that women find new jobs more quickly.

In any given month, the Labor Department considers every individual either employed, not employed but looking for a job, or neither (i.e., out of the labor force altogether).

Although more men are unemployed, the amount of time the average person is unemployed is the same for men and women. (And as you might expect, both sexes are spending more time unemployed than they did prior to the recession.)

The reason that men and women remain unemployed about the same time is that unemployed men and unemployed women are pretty similar in terms of their rates of finding a new job.

These flows help us predict whether women’s 49.9 percent share of payrolls will further increase, or ebb back. The implication: For the time being, women’s share of the work force seems to hinge primarily on continued contraction in manufacturing and construction.

Why? As I explained, more men are searching for jobs and, so far, the average male job searcher has been about as successful as the average female searcher. Once the male-intensive industries slow down their layoffs (even if those industries never actually expand again), more men than women will gradually find new positions — remember that more men are searching — and we will see women’s share recede from the 50 percent mark again.