What if the tax and benefits system already rewards marriage?

If you want the system to incentivise staying together, then relax.

MPs have written to the Chancellor this morning calling for the introduction of a marriage tax allowance. But what if the tax and benefits system already rewards marriage?

This would challenge the idea of the 'couple penalty' - the idea that the tax and benefit system makes it more attractive for families to split up than stay together. It's not mentioned in the MPs' letter, but it's an implicit part of the debate around the issue.

In principle, it sounds like a simple thing to work out: you would just need to calculate whether the system makes people richer if they split up, or not.

The problem is that it's relatively easy to work out how taxes and benefits change if a couple split up - but harder to work out how their cost of living changes. Economies of scale kick in when you live with a partner, and you need to calculate how much cheaper bills, rent and living expenses are under one roof.

The usual way of working out this is using an equivalence scale: a ratio that estimates how much extra family members cost. Most analyses that have suggested a 'couple penalty' exists rely on these scales, and usually an OECD scale drawn up in 1982. These scales generally rely on researchers' assumptions [pdf] about economies of scale and how people live - not, as a rule, actual evidence about how people live. They're not entirely plucked out of the air, but they are not really a meaningful way to assess relative need.

So why not ditch the abstraction, and actually aim to understand what people in the real world need to live on based on a common framework, and then work out the relative cost of living together or apart?

We need not imagine: this June some researchers did just that (report here [pdf]). Analysing what real, live, actual people said they need to live, and then combing through that to work out the precise cost of living, it found a rather different picture. An unemployed couple, for example, would be £62 a week worse off if they split up; if one parent was in work at £9 an hour they would £36 worse off; if both worked, it was £44. The numbers vary by family size and type but as a rule, people are not better off apart.

None of this necessarily makes the idea of marriage tax allowances a bad one, or undermines the aim of supporting families more generally. It does suggest extreme caution though. Policy based on a purely theoretical understanding of how couples manage money is likely to be ineffective policy. Examining the couple penalty is far from easy, but the best analysis we have suggests it doesn't exist on a systematic basis.

What's more, it suggests much of the angst about undermining marriage is misplaced. If you want the system to incentivise staying together, then relax, and rejoice: it already does.

Photograph: Getty Images

Gordon Hector is public affairs manager for the Joseph Rowntree Foundation.

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Geoffrey Howe dies, aged 88

Howe was Margaret Thatcher's longest serving Cabinet minister – and the man credited with precipitating her downfall.

The former Conservative chancellor Lord Howe, a key figure in the Thatcher government, has died of a suspected heart attack, his family has said. He was 88.

Geoffrey Howe was the longest-serving member of Margaret Thatcher's Cabinet, playing a key role in both her government and her downfall. Born in Port Talbot in 1926, he began his career as a lawyer, and was first elected to parliament in 1964, but lost his seat just 18 months later.

Returning as MP for Reigate in the Conservative election victory of 1970, he served in the government of Edward Heath, first as Solicitor General for England & Wales, then as a Minister of State for Trade. When Margaret Thatcher became opposition leader in 1975, she named Howe as her shadow chancellor.

He retained this brief when the party returned to government in 1979. In the controversial budget of 1981, he outlined a radical monetarist programme, abandoning then-mainstream economic thinking by attempting to rapidly tackle the deficit at a time of recession and unemployment. Following the 1983 election, he was appointed as foreign secretary, in which post he negotiated the return of Hong Kong to China.

In 1989, Thatcher demoted Howe to the position of leader of the house and deputy prime minister. And on 1 November 1990, following disagreements over Britain's relationship with Europe, he resigned from the Cabinet altogether. 

Twelve days later, in a powerful speech explaining his resignation, he attacked the prime minister's attitude to Brussels, and called on his former colleagues to "consider their own response to the tragic conflict of loyalties with which I have myself wrestled for perhaps too long".

Labour Chancellor Denis Healey once described an attack from Howe as "like being savaged by a dead sheep" - but his resignation speech is widely credited for triggering the process that led to Thatcher's downfall. Nine days later, her premiership was over.

Howe retired from the Commons in 1992, and was made a life peer as Baron Howe of Aberavon. He later said that his resignation speech "was not intended as a challenge, it was intended as a way of summarising the importance of Europe". 

Nonetheless, he added: "I am sure that, without [Thatcher's] resignation, we would not have won the 1992 election... If there had been a Labour government from 1992 onwards, New Labour would never have been born."

Jonn Elledge is the editor of the New Statesman's sister site CityMetric. He is on Twitter, far too much, as @JonnElledge.