administrative register data, which allows for analyzing the impact of individual, endogenous characteristics of the respondents such as preferences for doing specific activities. We find that the labour supply of fathers to preschool children is not different from that of young men without children, while there is a negative correlation between mothers to preschool children and young women´s labour supply. Comparing fathers and mothers to school children with those to preschool children, we find a positive correlation in both sexes labour supply. However, fixed effects estimations do not result in a reduction in mothers, nor in fathers, to preschool children´s labour supply indicating that there are some inborn characteristics for the other life-stage changes which are not revealed by doing ordinary cross-sectional analyses.