SWINS will develop and test a policy-oriented toolbox for the ex-ante assessment of the economic and social returns of investments in social services over the life course. Focusing on the complementarity of services aimed at developing human capabilities throughout the lifespan, it will explore the impacts of alternative social policy scenarios entailing different social services configurations (from maternal care and ECEC, to education and ALMP, up to long-term care). SWINS will conceptualize the returns to social services in terms of income, employment, and growth, as well as bridge knowledge gaps about how these investments influence macroeconomic stability and foster the EU sustainability transition performances. By implementing a right-based social investment approach, SWINS aims to support the rethinking of social services as drivers of the EUs shift towards sustainable wellbeing, going beyond their role as mere safeguards against the transitions side effects. SWINS methodology will be based on three main steps: 1) the identification of macro-regularities, that is the relation between investment in social services and aggregate social-economic performances, 2) analysis of the micro-foundations, that is the analysis of the micro-level mechanisms that explains the macro-regularities, 3) macro and long term projection of the results. SWINS will rely on a variety of methodologies, i.e. microsimulation analysis using the EUROMOD platform and its expansions, synthetic panels, causal analysis of comparative microdata, machine learning techniques and macroeconomic agent-based models. Leveraging the expertise of a multi-disciplinary (law, economics, sociology, political science) consortium, SWINS will explicitly pursue impact by proposing concrete strategies to integrate research findings and tools into the institutional, legal and policy frameworks.