Labor force participation of married women increased from 49.1% to 83.5% during the past 2 decades. By cross-section estimates on micro data of the probability of labor force participation in 1967, 1973, and 1980 and by using these estimates for predicting changes in labor force participation, we have found that increases in own wage has been by far the most important explanatory factor. Women's real wages have increased relative to husband's after-tax earnings both as an effect of the introduction of compulsory separate taxation in 1971 and as an effect of dramatically decreased sex differentials in pay partly associated with increased female education.