Everybody knows that politicians come from a privileged elite and govern in the interests of that elite. What's not so well-known is that this privilege does not consist merely in coming from a rich background. It also lies in the fact of the time of year in which they were born.

A new paper by Daniel Muller and Lionel Page shows that top US politicians are disproprtionately likely to have been among the oldest in their school year. This lucky accident of birth gave them advantages even many years later, partly because being among the oldest in their year made them likely to be bigger than their peers and so more likely to develop leadership skills. They say, following Heckman and Cunha (pdf): "Skills attained at one stage in life are self-productive in the sense that they facilitate further accumulation of human capital. This phenomenon may be especially pronounced for leadership skills."

This is consistent with research (pdf) by Elizabeth Dhuey and Stephen Lipscomb, who have found that American high school students who are old for their year are disproportionately likely to have leadershiip positions, such as presidents of clubs or sports team captains.

This is not an isolated finding. In Outliers Malcolm Gladwell describes (pdf) a strong relative age effect amongst sportsmen, so that those who are older than their peers are more likely to become top professionals; this benefits Americans (pdf) born early in the year and Englishmen (pdf) born in the autumn.

And researchers at the IFS have found (pdf) that people born in August - and so are the youngest in their year - do worse at school than those born in September who are the oldest in their year.

So, do the birthdays of British politicians corroborate Muller and Page's finding? Sort of. Of the 32 current Cabinet ministers, only one (Gove) was born in August; a random sampling would give us 2.7 August-borns. If we add the shadow Cabinet, we get four out of 63 August-borns; you'd expect 5.2.These numbers aren't so dramatic as to establish anything in their own right. But they are consistent with the notion that August is a disadvantageous time to be born.

This, I think, matters. It is more evidence of the importance that luck plays in determining our outcomes in life; nobody, after all, can control the timing of their birth. And so it further undermines the silly idea that the successful somehow deserve their wealth and power