The number of women working in the United States has grown steadily over the past 60 years. And more women have risen to the top, serving as CEOs, holding public offices, and even forcing “18 million cracks” in the nation’s highest glass ceiling during this year’s presidential campaign.

But a comparison of the number of working, married women in individual cities reveals a different story. In recent research with Natalia Kolesnikova (Federal Reserve Bank of St. Louis) and Lowell J. Taylor (Carnegie Mellon University), Professor Dan A. Black observed “two related, little-noticed features of U.S. labor markets.” First, the number of employed, married women, and their annual hours worked, varies significantly across cities. Second, the increase in the labor supply of married women differs among cities, both in magnitude and timing. “What is surprising about the picture is how different the paths are for two particular urban locations, New York and Minneapolis,” said Black.

These points were confirmed when Black and his coauthors examined Census data from 1950 through 2000 for white, married women in 50 U.S. metropolitan areas. The variation in employment rates held steady even when accounting for differing education levels and for women with and without children. For example, in Minneapolis, 79 percent of married women are employed, while only 49 percent are in New York. This disparity can be attributed to the fact that the labor supply of married women grew more rapidly over the last 60 years in Minneapolis than New York.

Black examined a variety of factors—local housing prices, child care costs, and local unemployment rates—but one stood out: commute times in metropolitan areas. Through an analysis of Census commuting time data and National Transportation statistics for the last three decades—the only period for which such information has been recorded—the authors found that on average women have a shorter trip to the office than men, and women with children commute even less. The cities with the longest commute times are New York; Washington, DC; and Chicago, and those with the shortest are Dayton, Oklahoma City, and Buffalo.

The authors predicted, and confirmed, that cities with longer commutes are associated with fewer married women who work—a link that is strongest for high school graduates. On average for this group, a one-minute increase in daily commute time appears to be correlated with 0.4 to 0.5 percent decrease in the labor force participation rate. Additionally, for high school graduates a longer commute reduces the total length of time that a married woman will work during her lifetime, but extends the number of hours she works each year. A one-minute increase in travel time is associated with an additional three to six hours of work annually.

Commute time length appears to have an even greater impact on women with children—with, again, the greatest effect on high school graduates, specifically with young children. A one-minute increase in a daily commute is coupled with a 0.66 percent decrease in the likelihood of employment. For high school graduates with children over the age of five, the probability of working shrinks by 0.44 percent, and with no children, by 0.24 percent. As might be expected, the effect of commuting time for college graduates with children is somewhat smaller as the earning potential for these women’s time at work is higher than high school graduates.

Overall, commuting time grew quickly during the 1980s with smaller increases—even decreases in some cities—through the 1990s. The average commute gained 27 minutes from 1980 to 2000. But the cities that experienced larger increases saw slower growth of numbers of working, married women. During this time, Austin only saw a 9 percent growth in female employment while Buffalo and Pittsburgh saw a 25 percent jump.

“The focus on married women is motivated by the fact that these women are most responsible for the large changes in female labor supply,” Black and his coauthors write. But, they believe these same conclusions would hold true for married men. The authors do, in fact, find that in metropolitan areas with longer commute times, married men work longer hours. Additionally, men who spend more time commuting are more likely to retire at an earlier age than men who live in cities with shorter commutes.

“This research represents only an initial attempt to document and investigate location differences in female labor supply,” the authors write. “Many related issues and questions remain for further investigation, both in future versions of this study, and in subsequent research.” Among the topics to be addressed, the authors cite a need for more evidence about causality by looking at natural experiments—such as large-scale construction projects and natural disasters—that affected commute times, but did not directly impact the behavior of workers.

Using the model for this research, it would also be possible to understand the variation in labor supply across cities due to tax and welfare policy. For example, the authors predict that if a city decreased income tax rates, women would be willing to work for lower salaries, and consequently there would be a larger increase in labor supply by married women in cities with shorter commute times.