Historically, job tenure stats reflect the cyclical behavior of the economy. According to a March 1990 article in The Journal of Economic History, brief jobs suggest a competitive market, while lengthy jobs suggest relatively sluggish wage responses to market conditions. Aside from that, understanding the numbers can be confusing at best-especially women-specific stats, since women’s gradual introduction into the workforce often includes interruptions for marriage and motherhood.

In the late nineteenth century, the average job lasted eight years; female cotton textile operatives worked for an average of 7.5 years, and female teachers stayed with employers for more than 13 years.

Fast-forward 100 years, when the typical job in 1982 also lasted eight years. Women’s jobs were shorter than men’s; one-quarter of all women older than 30 had jobs that lasted more than 20 years, but more than half of men were in near-lifetime jobs. (The Importance of Lifetime Jobs in the U.S. Economy, American Economic Review, Sept. 1982.)

In 1983, the rate at which women change occupations had increased substantially over the past two decades, but for men there had been no similar trend (Occupational mobility and job tenure in 1983, Monthly Labor Review, Bureau of Labor Statistics).

And by 1996, job-hopping had hit its stride. The median number of years spent with a current employer for those 25-34 was 2.8-three for men and 2.7 years for women.

A 2006 study analyzing U.S. employment trends confirmed that job tenure had fallen substantially since 1973. Interestingly, despite consistently high levels of turnover for all workers younger than 30, “job churning” after 30 was concentrated among men, while long-term employment became slightly more common among women. The pattern for females may reflect an increase in commitment to the labor force by women as they enter their 30s, the study noted (Is the Company Man an Anachronism? Trends in Long Term Employment in The U.S., 1973-2005 by Henry S. Farber, May 2006). It may also reflect the selection bias of women who are working during prime family-raising years, and their less heterogeneous job-seeking patterns.

The Bureau of Labor Statistics recently reported that the median employee tenure in 2010 was about 4.4 years-not to be confused with the total average number of years spent in any one job. (See this month’s FastCompany for more stats on the “four-year career.”)