Recent work by Lippman et al. (2020) examines the effect of German reunification in 1989 on gender and family norms, and show that female labor supply varies with husband-wife relative wage more in the West than in the East. In this paper, we try to understand what factors explain this fact. We first construct a cultural identity index from the attitude questionnaire in the GSOEP, with significant overlapping across East and West. We then build a search-matching/Nash bargaining model of marriage formation and divorce, and intrahousehold resource allocation, assuming same preferences in East and West, conditional on heterogeneous wages, education and cultural identity. We estimate 4 independent models in four 7-year periods (1992-1998, 1999-2005, 2006-2012, 2013-2019) using the GSOEP. The fit is good, so we can use the estimated model to measure how much of the observed differences between East and West (time uses and marriage sorting) are due to differences and changes in education, wages and cultural identity. Cultural identity is found to be the main factor before education and wages. It explains half of differences in time uses and marriage sorting on observables between East and West. Identity also interacts with education and wages (another 50% reduction).