Greece has cast off George Papandreou. Italy is about to send Silvio Berlusconi packing. The latest changes at the top of eurozone governments, which have been incapable of managing their debt, may prove to be no bad thing. Historically, however, there is a notable - albeit unscientific - correlation between the countries currently facing the wrath of the bond market and the average term-length enjoyed by their political leaders in the modern era.

Italians have been the most fickle of voters, it transpires, having been ruled by 39 prime ministers since establishing their modern constitution in 1946 - putting a new prime minister in place, on average, every 18 months or so.