The government is not prepared to let this latest crisis go to waste. In the aftermath of the riots, Iain Duncan Smith told listeners of the Today programme: "We have been ambivalent about family structure in Britain for far too long." This was a nudge and a wink to the long-standing Conservative commitment to marriage.
In 2007, David Cameron said that he would promote marriage as the "central institution in a strong society". Amid much controversy, the Conservative manifesto pledged to "recognise marriage in the tax system" by creating a transferable tax allowance, worth up to £150 a year, for 1950s-style married couples, in which one partner was a basic-rate taxpayer and the other earned less than £5,805 a year. The policy was costed by the Institute for Fiscal Studies (IFS) at £550m. It was estimated that less than a third of working-age couples would gain from it. The policy was a sticking point in the coalition negotiations, and even though it still formed part of the "Programme for Government", the Lib Dems have the right to abstain if it ever comes to parliament. The evidence suggests that they would do better to oppose it outright.
In 2006, research by the Institute for Public Policy Research found: "Stable and consistent parenting is more important than whether parents are married when predicting whether children will succeed in life." The report dismissed policies that focused support on old-fashioned family types, arguing that this would divert resources from those most in need. The IFS backed up these findings in July. In a new report, it spoke of "little or no evidence that marriage . . . has any effect on children's social or cognitive development".
It argued that, while "it is true that children born to married couples are, on average, more cognitively and emotionally successful than children born to cohabiting couples . . . careful analysis shows that this largely reflects the differences between the types of people who decide to get married and those who don't".
Even if the policy did have a social benefit, it is unlikely that such a small bung would do much to raise marriage levels. The last time the Tories were in power, Norman Lamont and Ken Clarke had the sense to restrict the scope of the Married Couple's Allowance, which the latter called an "anomaly". Cameron and Duncan Smith misunderstand the evidence and confuse correlation with causation. They are moralising about family types and harking back to a divisive policy that will do little to improve a child's life chances - or prevent a riot.
Will Straw is an associate director of the Institute for Public Policy Research