Why marriage isn't the main bond that keeps couples together

The findings, by the politically neutral Institute for Fiscal Studies (IFS) reveal that relationship stability is mainly determined by other factors, including age, education, occupation and income, plus delaying and planning pregnancy, rather than the institution of marriage itself. These same factors are also influential in whether people opt to marry.

In other words, people who marry are likely to be older, better educated and wealthier than those who have babies out of wedlock, and much of the difference in stability of relationships between married and cohabiting couples is down to the kind of people who get married before having children and those who opt to live together.

The IFS said the research casts doubt on the Government's aim of promoting marriage in order to reduce the rate of parental separation, challenging the view that it is marriage which, of itself, provides the bedrock for family permanence.

The IFS analysis was carried out by Alissa Goodman and Ellen Greaves and is published in its briefing paper Cohabitation, Marriage and Relationship Stability. It interprets data from the Millennium Cohort Study (MCS) – a national longitudinal study of a sample of children born in 2000 and their parents.

The analysis highlighted that while cohabiting parents were more likely to split up than married ones, there was little evidence that marriage was the cause of greater stability between parents, or that encouraging more people to get married would result in fewer couples breaking up.

According to the IFS's findings, parents who were cohabiting when their child was born were three times more likely to split up by the time their child was five than married parents (27 per cent compared to nine per cent).

However, cohabitees were also typically younger, less well off, less likely to own their own homes, have fewer educational qualifications and were less likely to plan their pregnancies than married people. Once the differences between the two groups were accounted for, the difference in the likelihood of separation reduced to two percentage points.

It concluded that while married couples have more stable relationships than couples who live together, this was not due to the fact that they were married, but because of the other characteristics that had that led to marriage.

Ellen Greaves, research economist at the IFS, said: "The evidence suggests that much of the difference in relationship stability between married and cohabiting parents is due to pre-existing differences between those who get married before they have children, compared to those that cohabit." The IFS findings contradict the Government's own analysis, published in its recent State of the Nation report, which said that three million children in the UK had experienced the separation of their parents and this was partly attributable to a rise in cohabition, given the increased likelihood of break-up for

cohabiting couples relative to married couples.

David Cameron has said that the Conservative Party will "celebrate and encourage marriage" and has promised a transferrable tax allowance for married couples.

The IFS report says: "It seems simply that different sorts of people choose to get married and have children, rather than to have children as a cohabiting couple, and that those relationships with best prospects of lasting are the ones most likely to lead to marriage. Our analysis suggests, therefore, that if more cohabiting parents decide to get married, it is very unlikely that a significant number would become more likely to stay together. It also means that it is highly unlikely that the increasing rate of childbearing among cohabiting couples has caused an increased likelihood of break-up among parents."

Dr Katherine Rake, chief executive of the Family and Parenting Institute, said: "The evidence base for it being marriage per se that creates stability for couples does not appear to be there."

On the subject of proposed tax breaks for married couples, she added: "There is no evidence that the tax break would have any impact; it is going to be increasingly difficult for the coalition Government to justify an extra spend on something that has no proven effect at a time when there are severe and considerable cuts across the budget."