What explains the East-West gap in part-time employment in Europe?

I investigate differences in the incidence of part-time employment between Central and Eastern European (CEE) countries that have joined the EU since 2004 and Western European countries. I estimate employees probabilities of working part time based on observable characteristics, including capital income and market hourly wages. While labour force structure and economic development help explain more than half of the East-West gap in voluntary part-time employment, the remaining unexplained gap amounts to 10.6 percentage points for women and 1.0 percentage point for men. I find that progressivity in personal income taxation is a significant predictor of voluntary part-time employment, but has a limited impact on the unexplained East-West gap, reducing it by 0.7 percentage points for women and by 0.3 percentage points for men. The perceived importance of work and leisure time also have predictive power overall, but these social values do not explain the East-West gap. Moreover, full-time employees in CEE countries do not report stronger preferences for part-time employment than their Western European counterparts, suggesting that differences in working hours norms may play a more important role than hours constraints imposed by firms. Finally, evidence from German reunification supports the view that informal institutions may play a more important role than formal institutions, as the unexplained East-West gap in voluntary part-time employment gradually narrowed over time.