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



For many reasons, women are paid less than men. One is that many women have jobs with more desirable schedules.

Last week I wrote about how more women than men have been employed in payroll positions during the winter months of this recession, and how in April 2010 men regained their majority, with 50.04 percent of payroll positions. However, if you are reading this between 9 a.m. and 5 p.m., there are probably more women at work than men.

The chart below displays information about the work force by time of day, based on surveys conducted by the United States Census Bureau in 1997, 2001 and 2004 (when the 2010 Census is finished, an analysis like this will be possible for 2010). The calculations in the chart are based on work on gender segregation I have been doing with Christian Ferrada, a University of Chicago graduate student.

Casey B. Mulligan

The black series shows the number of full-time people ages 18 to 65 who are at work in nonfarm jobs at each time of day, excluding people who work from home more than eight hours a week. Not surprisingly, it is vastly more common to be at work between 9 a.m. and 5 p.m. than to be at work in the evening or early morning.



The solid pink series displays the fraction of people at work at each time of day who were women, and the dashed pink shows the fraction for the entire day (weighting by the number of people at work). For example, only 32 percent of people at work at 7 a.m. were women, compared with 42 percent for the entire day.

An important reason for the time-of-day pattern of women’s share at work derives from the fact that men are more likely to have jobs that require early arrival at, or late departure from, work.

Interestingly, during the middle of the day the female share was 44 percent — two percentage points higher than the average for the entire day during the years studied. Given that 50 percent of payroll employees in April 2010 were female, we might expect that women in April 2010 would be as much as 52 percent of payroll employees at work at any time between 9 a.m. and 5 p.m. — a clear majority.

By the same logic, I expect that early in the morning or late in the evening women were nowhere a majority of employees at work, even during this recession when women were often a majority of payroll employees.

The vast majority of workers perceive work from 9 a.m. to 5 p.m. to be more desirable than work during the off-hours, and many of the off-hours workers are compensated with higher pay for the less desirable schedule. A variety of factors — including, some economists and many women’s rights advocates say, gender discrimination — may cause women to be paid less than men, but part of the reason may be the hours they choose to work.