Why £1,000 a year to get married? Is it "for the sake of the children"?

I ask this question - especially to any Conservatives in the audience - because I have just read in Levitt & Dubner's excellent book Freakonomics that, once you control for other factors, your family structure has almost no effect on educational and social outcomes.

That's right - according to their research, once you control for other factors it really doesn't matter whether you have a mum and a dad, one mum, one dad, or two mums or two dads. What does matter is the socioeconomic background of your parents.

David Cameron is falling into a classic lazy intellectual trap when he says:

"We have the highest rate of family breakdown in Europe. And we have the worst social problems in Europe. Don't tell me these things aren't connected."

Cameron has come down with a bad case of post hoc ergo propter hoc. Of course those things are connected. They are strongly correlated, and that is borne out both by the data and anecdotal experience. But that doesn't mean they are cause and effect.

In fact, Levitt & Dubner's research suggests that a poor socioeconomic background makes you both more likely to come from a broken home and more likely to fail at school. Encouraging people to marry when they otherwise wouldn't have is rather like rearranging the deckchairs on the Titanic.

It is poverty and ignorance themselves that cause the social strife we are seeing around us. The only way out of it is increasing social mobility - and the key to unlocking social mobility is education itself.

But we knew that, didn't we?

Update: Teh Grauniad makes much the same point this morning.
(Hat tip: Paul Walter.)