The Big Apple likes to see itself as the heart of capitalism where business can be conducted at all hours. But a sizable chunk of the New York City-area population has quietly managed to keep itself out of that rat race.

If you're a married woman living in the New York City area, there's a better than 50 percent chance that you don't work, according to a recent analysis of Census data by economists affiliated with the St. Louis Federal Reserve Bank.

More specifically, only 49 percent of white high school-educated married women in their prime working ages were holding down jobs in the New York area as of the 2000 Census. To put that in perspective, there are roughly 2 million woman over 15-years-old who are married in the New York area.

The national average for this particular demographic is 67 percent. At the other end of the spectrum is Minneapolis where almost 80 percent of these married women are employed -- that's larger than the percentage of working men aged 25 and older in the U.S.

And the phenomenon isn't a recent one. Since the 1970's married women in the Twin Cities have been living by the Protestant Ethic more than their New York counterparts. (The disparity isn't as drastic if you only look at college-educated married women -- highest rate goes to Albany with 80 percent and lowest to Honolulu with 64 percent -- but it's still there.)

The chart below shows the percentage of white high school-educated married women in the labor force between 1940 and 2000 (data for 1960 are missing):

So what explains the difference? Do married women in New York just like to bust their butts less?

The researchers, Dan Black of the University of Chicago, Natalia Kolesnikova of the St. Louis Fed Reserve Bank, and Lowell J. Taylor of Carnegie Mellon University, looked at the most obvious factors that could be responsible: wages, housing costs, and labor market conditions. In places where home prices or incomes are high, or the employment rate is low, you'd expect higher employment rates. But they found little evidence that these factors are influential at all.

Child-care costs also don't seem to be a big factor since married women with and without children exhibit the same patterns.

Married women in New York and Minneapolis seem to be taking into account some things that are specific to their cities when deciding to work or not. Surprisingly, the economists argue, the most important specific thing seems to be traffic.

Take a look at the table reproduced from the paper at the bottom of this post. You'll notice that cities similar to New York in the percentage of married women who work are also the cities with the most traffic congestion.

Time spent in traffic is costly, so as congestion increases there may be a certain point where married women decide to either drop out of the labor force or not join it in the first place. The data seem to back this up.

Looking back over time, "Cities in which commuting time increased most rapidly generally also experienced slower growth in female labor force participation," write the researchers.

As for the women who are employed, rising congestion seems to go in hand with working more hours. If commute times increased by one minute, the researchers found that married women spent an additional three to six hours working per year.

The same thing happens for men. If the commute time is longer by 20 minutes in one city compared to another - that's close to the difference between Nashville and New York -- then a man in NYC is likely to work an extra week each year.

And if you work longer, you might want to retire earlier too. While the results aren't overwhelming, it turns out that a man that lives in a city like New York is 1.3 percent more likely to be retired when he's in his 50's and 60's than a man living in a city like Nashville.

It's important to note that the findings show correlation and not causation. Still, the evidence is consistent with the idea that longer commute times are influential factors in keeping some married women at home and other married men and women laboring longer.

And for those of us in New York, it adds one more reason to be upset that plans for congestion pricing are dead.

UPDATE
Some people have been wondering why the study only looked at white women, so I asked Kolesnikova about it. She says it comes down to sample size: There aren't enough non-white women in the metropolitan-level Census data to run tests on.

(Photo credit: Bettmann/Corbis)