The European experience of convergence reveals that the catching up of some peripheral countries takes place by an increase of their regional disparities. In a way there is a tension between growth and social cohesion. That is particularly worrying for the socio-economic balance of the European Union when one expects that the enlargement to the Central and Eastern European countries will introduce more heterogeneity in space. Is public intervention able to reduce this tension and to seek at once more efficacy and more cohesion, i.e. equity? The aim of this article is to model public intervention in its two dimensions. The first is a search for efficacy through expected increased returns, i.e. productivity gains resulting from agglomeration forces. The second is a search for some collective gains that arise from a preservation of social cohesion by limiting disparities. Tax rates, fiscal incentives and capital grants are not the only public determinants of firm’s location choice. Public expenditures and economic infrastructures also play an important role on location behaviours. Regions compete by offering fiscal incentives and by supplying public goods in order to attract mobile capital. Our approach rests on several recent contributions. Models of effective taxation, in particular the seminal work of King and Fullerton (1984), have proved to be an appropriate framework to assess the impact of fiscal and financial incentives on firm’s investment decisions. In addition, two inspiring studies provide us with an elegant way to take into account both agglomeration economies, which stimulate collective efficacy [Garcia-Milà and McGuire (2002)] and the reduction of interregional disparities [Garcia-Milà and McGuire (2004)]. The key factor in this analysis is the solidarity level between regions. The approach could make the trade-off between efficiency and equity more explicit. These theoretical and methodological contributions are then subject of an application to the Belgian economy and its regions, at the heart of the European issues.
