How does human capital affect partnership transitions? Evidence of complex contingencies in a multi-country sample. Giulia Ferrari and Ross Macmillan Abstract Second Demographic Transition highlights three broad social currents: intimate relationships are increasingly unstable and contemporary life courses typically involve multiple partnerships, educational attainment has rapidly expanded and has reconfigured context of relationship formation and their meaning, and adult roles of school, work, and family increasingly overlap and compete in complex ways. Building upon these themes, we differentiate opportunity costs of education with human capital enhancement to better understand the role of education in relationship formation. Our empirical analysis on nine European countries stresses the importance of human capital accumulation in accelerating relationship transitions. Specifically, the results show that time to entry into first partnership is significantly slowed by higher educational attainment, while, on the contrary, human capital accumulation is an asset for subsequent unions. However, results also show that aspect of prior relationships, independent of human capital, can be a detrimental to entry into subsequent unions. Keywords Second Demographic Transition, relationship formation, education 1 Giulia Ferrari, Carlo F. Dondena Centre for Research on Social Dynamics, Bocconi University; email: giulia.ferrari@unibocconi.it Ross Macmillan, Carlo F. Dondena Centre for Research on Social Dynamics, Bocconi University; email: ross.macmillan@unibocconi.it