International trade is hampered by a variety of administrative barriers (Bratt, 2017;Carrère & Melo, 2011a). These hurdles seem to persist even when countries form regional trade agreements (RTAs;Hornok & Koren, 2015). Several studies show that a reduction in administrative barriers increases trade volumes (Carrère & Melo, 2011b;Engman, 2005), which motivated the members of the World Trade Organization (WTO) to sign the Trade Facilitation Agreement (TFA; WTO, 2014). However, the majority of WTO agreements, RTAs and the TFA focus on trade in goods. In contrast, the General Agreement on Trade in Services (GATS, 1995), also signed by the WTO members, provided only very little progress in terms of reducing administrative barriers regarding service trade (Adlung & Roy, 2005;Hoekman & Mattoo, 2013;Mustilli & Pelkmans, 2013). Administrative hurdles are especially problematic in the case of services, because the main impediments to trade are not tariffs or shipping costs, but regulations and entry barriers for service providers (Baldwin, 2011). Furthermore, only one per cent of RTAs signed between 1950 and 2010 target services specifically, and more than half of the almost 600 agreements do not even mention services (Dür et al., 2014). Services are in many countries highly regulated, and the access to service markets is often restricted, that is, via licence and qualification requirements, entry quotas or even discriminatory regulations regarding the nationality and residence. Since restrictions for the same service differ between countries, a service exporter needs to fulfil country-specific regulations for each and every host market (OECD, 2018).These issues exist even in highly integrated markets, like the European Union (EU;Felbermayr & Jung, 2011;Mustilli & Pelkmans, 2012). Kox and Lejour (2006) argue that the principle of free movement of services in the EU is still far from being complete. The heterogeneity in regulation and rulesThis is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.