But one of its proposals has attracted genuine interest from across the world: The idea of a "citizens' income." This concept (a less radical version of the "universal basic income" scheme tried out by Finland) could in theory appeal to both the left and the right; the former because it might reduce inequality, and the latter because it could simplify social security.

After a long gestation, Five Star is rolling out its plan in Italy. Unfortunately, the plan has little of the revolutionary spirit of Milton Friedman's idea for a simple guaranteed basic income for all citizens, jobless or not, and is more like a classic welfare-to-work program. After a deep recession and weak recovery, there's a strong case for helping Italy's left-behind. The worrying thing is that this experiment becomes an administrative nightmare, making it harder to target those most in need.

Italy's new citizens' income is for households earning less than 9,360 euros ($10,612) a year. It's made up of an income support scheme and a housing allowance, which can add up to 780 euros a month for a single person with no income. It is aimed at pensioners and people of working age. The latter must be willing to accept a suitable job, or else lose the benefit – hence its difference to more radical basic income schemes. Companies will get a discount on their social security contributions when they hire a citizens' income recipient.