The prospect of ten countries joining the European Union on 1 May 2004 provoked fears that the Union’s decision-making would become more unwieldy, even paralysed by the arrival of the newcomers. These were fears about numbers – moving from 15 to 25 was indeed a big deal – but also about attitudes. As we suggest elsewhere in this special report, the new member states had a distinct view of their neighbours, of their history and of their own position in the world. They tended to be more interested in Russia and eastern Europe than in Europe’s former colonies, and more in democracy and freedom than in stability and the status quo. The invasion of Iraq in 2003 brought some of these divisions between ‘old’ and ‘new’ Europe into sharp relief.

Beyond these concerns about political issues, it was also feared that the somewhat clubby, consensus-focused decision-making between the 15 pre-2004 member states in the Council of Ministers would be gridlocked. There was also the question of whether new member states would be able to supply sufficient numbers of officials to staff the Union’s institutions. Ten years on, there is little evidence that the addition of ten new member states has led to gridlock in EU decision-making. Politically and institutionally, the Union has become more diverse without experiencing major hiccups in the process.

Hard data on voting by the member states is hard to come by. The Council of Ministers tends to take decisions by consensus rather than a recorded vote even after the Lisbon treaty’s expansion of majority voting to additional policy areas. At the same time, voting records often mask persistent policy disagreements among the member states. Nevertheless, based on the data that is available, a report by VoteWatch published last year suggests that the 2004 entrants have not been more troublesome than the older member states – quite the opposite. The member state that voted against the majority most often is, not surprisingly, the UK. It is followed by Germany, Austria, Denmark and the Netherlands – none of them a new member state.

At the other extreme – member states that most often voted with the majority – are France and Lithuania, followed by Cyprus, Greece, Finland and Latvia, a group that includes three of the 2004 enlargement states.

Such statistics do not capture the high-profile cases that most shape perceptions. For example, in 2012, Poland blocked an energy roadmap outlining climate targets, out of concern for its coal-fuelled power plants, forcing the other member states and the European Commission into a work-around in order to continue progress toward cleaner energy.

But such instances are quite rare, and for every new member state taking a confrontational approach there is an example of an old member state doing the same. Hard lobbying for national concerns and defence of red lines is hardly the preserve of the newcomers. For every Cyprus blocking chapters in Turkey’s accession talks there is a France or an Austria blocking as well.

In a 2007 paper reviewing existing research on the post-enlargement workings of the EU’s institutions, Helen Wallace, a scholar of Europe, suggested that on the whole, business as usual prevailed in EU law-making; in particular, while there were some changes in the Council’s work, there is no evidence of a shift away from consensus decision-making or of new member states being particularly reticent about legislation in specific policy areas.

In fact, the prospect of enlargement drove some reform to the Council’s procedures in 2002, when the EU adopted the ‘Seville reforms’ that were supposed to streamline the Council’s work and make it more effective.