The obligation to carry out an ex post evaluation of certain State aid measures was introduced in the European Union in 2014. This obligation represents an important element of the broader State Aid Modernisation initiative of DG Competition. In this article, we offer guidance, both from a legal and an economic perspective, on when an ex post evaluation is required, which methods are available and which methods are actually considered by Member States. More specifically, we propose a ‘traffic light system’, supporting a self-assessment of whether an ex post evaluation is required for a specific measure or not. Furthermore, we review the 24 evaluation plans which were approved by the European Commission by August 2018, with respect to the proposed approaches to the measurement of direct and indirect effects, appropriateness and proportionality. We find that the most common method considered by Member States in their evaluation plans is the econometric estimation of differences-in-differences.
Keywords: State aid ex post evaluation; Environmental aid; Econometric estimation methods; Evaluation plans.