The goal of open government data (OGD) initiatives is to promote transparency, efficiency and public participation in public management policies. To do so, public organizations must consider which elements might help the development of their open government data portals (OGDP). This paper studies the evolution of OGDP in the 28 countries of the European Union (EU) in a multidisciplinary setting. Whereas the comparative frameworks in the literature are mostly based only on technological parameters, this exploratory research aims to uncover which factors might uphold the successful development of OGDP through the analysis of the relationships between a number of technical and socioeconomical indicators over a period of three years (2015-2017), using a clustering methodology. The results show that EU countries are slowly homogenizing their OGD approaches into two currents/speeds, based mainly on economic factors and open government development status. The originality of this research lies in the sense that it provides not only a technical benchmark, but also a longitudinal and multidisciplinary perspective that will add to the current formulation of OGD policies and practices in any international setting.