"The seven-fold increase, since 1920, in the labor force participation rate of married women [in the United States] was not accompanied by a substantial increase in average work experience among employed married women. Two data sets giving life-cycle labor-force histories for cohorts of women born from the 1880s to 1910s indicate considerable (unconditional) heterogeneity in labor-force participation. Employed married women had substantial attachment to their jobs; increased participation brought in women with little prior work experience. Average work experience among cross sections of employed married women increased from 9.1 to 10.5 years over the 1930-50 period. Implications for 'wage discrimination' are discussed."