  Nowadays innovation is one of the main determinants of economic development.
Patents are a key measure of innovation output, as patent indicators reflect
the inventive performance of countries, technologies and firms. This paper
provides new insights on the causal effects of the enlargement of the European
Union (EU) by investigating the patents performance within the new EU member
states (EU-13). The empirical results based on data collected from the OECD
database from 1985-2017 and causal impact using a Bayesian structural
time-series model (proposed by Google) point towards a conclusion that joining
the EU has had a significant impact on patents performance in Romania, Estonia,
Poland, Czech Republic, Croatia and Lithuania, although in the latter two
countries the impact was negative. For the rest of the EU-13 countries there is
no significant effect on patent performance. Whether the EU accession effect is
significant or not, the EU-13 are far behind the EU-15 (countries which entered
the EU before 2004) in terms of patent performance. The majority of patents
(98.66\%) are assigned to the EU-15, with just 1.34\% of assignees belonging to
the EU-13.
