if tuition fees vary across institutions and fields of study with different curricula costs and returns students are more likely to go into the fields and institutions that will give them better chances of success in the labour market oliveira martins et al while private returns largely reflect wage and employability premia stemming from additional years of schooling for an individual social returns focus on productivity gains at the aggregate level in this respect social and private returns differ markedly if there is a purely signalling role of education andor there are substantial human capital spillovers