The role of the Social Economy (SE) in society is increasingly acknowledged by social agents and institutions, especially in the context of the 2030 Agenda for Sustainable Development. Commitment to SE requires the support of quantitative measurement of its contribution to society from an aggregate perspective. The difficulty in specifying it in quantitative terms is related to the assessment of the contribution of SE's differentiating and intrinsic values. These values contribute to the fight against some structural problems that persist in modern society in terms of unemployment, inequality, territorial imbalance, environmental problems and social exclusion that surpass the economic sphere and involve the contribution to social goals, social utility and social and territorial cohesion. Our objective is an assessment in quantitative terms, including an estimation, in monetary terms, of the specific contribution of Social Market Economy (SMkE) firms to society linked to their distinctive principles, and thus their behaviour, in comparison to traditional profit-oriented firms, used as a control group. We use impact analysis techniques, with a simulation exercise, by which SMkE entities "lose" their identity and behave like profit-oriented firms. The results obtained for Spain confirm the existence of differential behaviour that generates social value in several ways. In monetary terms, in 2017, SMkEs contributed 6,229 million Euros in benefits to Spanish society that would have been lost if SMkE entities had behaved like profit-oriented firms.