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The Extraordinary Effect of Marriage

30th September 2013
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Marriage has powerful and beneficial effects on human beings. Finding that special someone can really do wonders! A new branch of research that looks more closely at marriage has helped statisticians work out why the effect of marriage is so extraordinary! Andrew Oswald, Professor of Economics at Warwick University, discusses his findings.

The work proceeds in a way common in modern social science. Large random samples of families are followed through time. They are interviewed every year about their lives, and their incomes and psychological well-being levels are measured.

The first finding is that marriage makes you richer

In virtually every country ever studied, workers who are married earn between 10% and 20% more than those who are single. This figure holds after many other influences are factored out (in other words, it bears in mind there are lots of other forces that affect pay, including someone's age and education and gender and so on).

Economists argue about what this finding means. Some say that it is because 'better' people - healthier, more tenacious, more conscientious, better looking, more productive, stronger - are the ones who get married. Marriage itself, on this line of argument, is not doing anything to a man or woman's earning power. Those with large pay packets simply choose to get hitched more than those on low earnings.

That sounds plausible, but actually it does not fit the facts. For one thing, if you study people in their early 20s, then those who are married barely earn more than singles. It appears that the 'marriage wage premium', as it is sometimes called by researchers, actually gets stronger through time as the years pass and the marriage gets longer. This suggests that marriage is more a cause than an effect of higher pay.

One possibility is that marriage makes you work harder because you want to impress and hang on to your spouse. Evolutionary biologists are fond of reminding economists that they think Darwin explains everything: deep down human beings are just nest-builders and mate-chasers. They may be right.

Marriage makes you live longer

The second main finding from modern statistical research is even stranger. Although most members of the general public are probably not aware of it, there is now some consensus among epidemiologists that you can prolong your life by marrying. Marriage keeps you alive about 3 extra years, on average.

Numerous studies have shown this and one of the most intriguing followed male graduates of Amherst College in the United States in the late nineteenth century. At age 18, all these men had their health, height and weight measured. Their later occupation was also recorded, and much else about them. Then they were followed through their lives. All are now dead, of course. Strikingly, those who married lived much longer, even bearing in mind other influences.

There is plenty of British evidence too. In the late 1960s, 20,000 middle-aged male civil servants had a medical examination and were then tracked for the next two decades. At the end of that time, 14 out of every 1000 married men had died, compared to 21 for widowers, 17 for those single, and 21 for those separated. This study is interesting because it appears to pin some of the blame, if that is the right word, on cardiovascular disease. Unmarried men had much higher blood pressure.

The current conventional view in the epidemiological journals is that marriage works through some kind of protective effect on mental well-being. It lowers stress and worry - presumably because sharing worries halves them, just as tradition says. Partly, too, married people smoke less and eat in a healthier way.

My colleague, Jonathan Gardner, and I had been following a group of many thousands of British men and women through the 1990s. Sure enough, whether they were married at the start of our data, in 1991, is a fairly good predictor of whether they are alive by the end of the decade. That appears especially true for women. Even we have been startled by the size of the marriage effect on mortality risk. It appears in some cases to be nearly as large as the risk from smoking. In other words, if you must smoke, make sure you are married. It would be fair to say we do not have a detailed theory for why it is dangerous to be unmarried.

Marriage also moulds mental health and happiness

Here the effect is large. A New Jersey study followed large numbers of individuals for a decade. It measured the subjects for depression. After allowing for many other factors, including health at the start of the period, marriage greatly reduced the probability of later depression. Interestingly, the quality of the marriage was the best predictor of overall mental health in later years.

Do you have to be formally married to get the mental and physical health benefits of marriage? No, but it appears to help. Looking across statistical studies, it seems that cohabiting brings some but not all of the protective effects of marriage.

How about second and third marriages? They bring less protection to a human being than the first marriage. This is what you might expect, if you think that the very best marriages are the ones that automatically survive intact. Second and third marriages bring a great deal of happiness, according to research, but not as much as first, lasting marriages.

Sorry, I'm taken.

Andrew Oswald, Professor of Economics, Warwick University.