We propose a bootstrapped Data Envelopment Analysis (DEA)-based procedure to pre-calculate and pre-evaluate the short-run operating efficiency gains of a potential bank merger or acquisition (M&A). As an illustrative example, we apply our proposed procedure to investigate the degree of operating efficiency gains of 45 possible bank M&As in the Greek banking industry over the period from 2007 to 2011. The results reveal that a year before and a year after the initiation of the Greek fiscal crisis, the majority of the potential bank M&As under examination were unable to generate short-run operating efficiency gains. In addition, our results for 2011 indicate that the majority of bank M&As can lead to short-run operating efficiency gains. Finally, the empirical findings support the view that a merger or acquisition between efficient banks does not ensure an efficient bank M&A.

This paper examines the bank productivity growth and integration process for the 28 EU countries during three main phases of the financial crisis: the U.S. subprime crisis (2007–2008), the global financial crisis (2009–2010) and the sovereign debt crisis (2010–2012). We extend the Malmquist Productivity Index by applying an additive two-stage DEA model. This allows us to explore the sources of growth in different stages of production. Furthermore, we assess the integration of European banks by analyzing the β-convergence and σ-convergence of the two-stage Productivity Index. Our results show a productivity growth during the U.S. subprime crisis, but a consistent decline during the global financial crisis. The loss of competitiveness of the European banking system is due to the drop in growth of the performance stage and technical change. Finally, we find a strong convergence pattern during the financial crisis, mainly driven by the catch up process of some Eastern countries and the drop in performance of Western countries.