REFERENDUMS are spreading across Europe. During the 1970s only around two were held, on average, each year. Now about eight take place annually. In June Britain will hold a referendum on whether or not to leave the European Union. In October Italy will hold a referendum on constitutional changes. Meanwhile in Hungary, Viktor Orban, the prime minister, has called a referendum asking the question: "Do you agree that the European Union should have the power to impose the compulsory settlement of non-Hungarian citizens in Hungary without the consent of the National Assembly of Hungary?" Despite their seeming popularity, referendums are not always a good idea—why? Fans of direct democracy argue that referendums offer a way to engage voters. Support for mainstream parties has tanked in the rich world. Referendums on issues can get people interested in politics. When held regularly, as in Switzerland, they can also serve to educate voters; each time the Swiss head to the polls they get a neat booklet laying out the issues, replete with charts and diagrams. When Ireland voted in a referendum to approve same-sex marriage last year, fully 61% of the population turned out to vote, with hundreds of young expatriates who were still on the electoral rolls boarding planes to take part. A referendum in Scotland on whether or not to become independent from the rest of the United Kingdom also saw young people, not usually so fond of politics, getting involved enthusiastically.

But increasingly, referendums are being used as a more troublesome political tool. Some, including the one in Hungary, have been called to challenge or subvert EU policies. Last year Alexis Tsipras, Greece's prime minister, called a referendum with only eight days' notice on the Greek bail-out conditions. Elsewhere, populist single-issue groups are using referendums as a way of challenging EU-wide treaties: in April a referendum was held in the Netherlands on the EU's trade deal with Ukraine, although the Netherlands is not going to be much affected by it one way or the other. Mr Cameron's referendum was partly due to pressure from Eurosceptics within his own Conservative Party worried by the rise of the UK Independence Party. And they can be used by politicians keen to avoid making tricky decisions which may be unpopular with their own party. In Australia, for example, a conservative government is putting the question of whether or not same-sex marriage should be legal to a referendum, despite popular support for the measure. This is an expensive way to push through the reform: PwC, a consulting firm, reckons that the plebiscite could cost $525m Australian dollars ($380m), including an estimated $158m to conduct the voting and $66m for campaigning.

According to data from the Centre for Research on Direct Democracy, a Swiss think-tank, the median turnout for nationwide referendums has dropped from 75% in the early 1990s to 43% in the past few years. If mainstream politicians continue to call them in order to seem democratic—yet appear unable to deliver on their promises (as with Mr Tsipras)—voters will become even more disengaged. So too if they continue to be exploited by fringe groups or populist politicians. Rather than boost voter engagement, the current rash of referendums may end up having the opposite effect.