Trading kidneys, repugnant markets and stable marriages win the Nobel Prize in Economics

Roth and Shapley charted a course for economists to go beyond simply arguing for markets in everything.

The 2012 Nobel Prize in Economics - technically the Sveriges Riksbank Prize in Economic Sciences in Memory of Alfred Nobel, but nobody cares - has been awarded to two American Economists, Alvin Roth and Lloyd Shapley "for the theory of stable allocations and the practice of market design". The Nobel Committee explains what that means:

This year's Prize concerns a central economic problem: how to match different agents as well as possible. For example, students have to be matched with schools, and donors of human organs with patients in need of a transplant. How can such matching be accomplished as efficiently as possible? What methods are beneficial to what groups? The prize rewards two scholars who have answered these questions on a journey from abstract theory on stable allocations to practical design of market institutions.

Lloyd Shapley used so-called cooperative game theory to study and compare different matching methods. A key issue is to ensure that a matching is stable in the sense that two agents cannot be found who would prefer each other over their current counterparts. Shapley and his colleagues derived specific methods – in particular, the so-called Gale-Shapley algorithm – that always ensure a stable matching. These methods also limit agents' motives for manipulating the matching process. Shapley was able to show how the specific design of a method may systematically benefit one or the other side of the market.

Alvin Roth recognized that Shapley's theoretical results could clarify the functioning of important markets in practice. In a series of empirical studies, Roth and his colleagues demonstrated that stability is the key to understanding the success of particular market institutions. Roth was later able to substantiate this conclusion in systematic laboratory experiments. He also helped redesign existing institutions for matching new doctors with hospitals, students with schools, and organ donors with patients. These reforms are all based on the Gale-Shapley algorithm, along with modifications that take into account specific circumstances and ethical restrictions, such as the preclusion of side payments.

Even though these two researchers worked independently of one another, the combination of Shapley's basic theory and Roth's empirical investigations, experiments and practical design has generated a flourishing field of research and improved the performance of many markets. This year's prize is awarded for an outstanding example of economic engineering.

The committee have yet again reaffirmed the old adage that the most important thing to do when trying for a nobel prize is to live long enough that your achievements are recognised. The Gale-Shapley algorithm, for instance, was devised in 1962, when Lloyd Shapley was 34. It concerns a maths problem known as the stable marriage problem: if you have an even number of men and women, can you always come up with a set of marriages where there are no two people of opposite sex who would both rather have each other than their current partners? (1960s maths problems: usually heteronormative.) If you can, then the marriage is "stable".

The Gale-Shapley algorithm is a way of always ensuring stable matches; and much of Shapley's work covers the same areas, straddling the boundaries between economics, mathematics, and computer science.

Roth is the younger of the two winners, and works in a far more empirical sphere. As the committee points out, although the two men never actually collaberated, Roth took Shapley's theoretical work and applied it to actually existing markets. For instance, Roth used the Gale-Shapley agorithm to ease the kidney shortage in the US. David Wessel explains (£):

As of noon yesterday, 58,470 people in the U.S. were waiting for a kidney transplant. Most won't get one this year. There aren't enough donated kidneys to go around. Surgeons transplanted just 15,129 kidneys last year. Now a band of transplant surgeons and economists are trying to fix that by creating a moneyless market for exchanging kidneys. Most transplanted kidneys come from a person who has died, a supply that grows slowly because of ignorance about the need for donations or grieving relatives' reluctance. But a kidney taken from a live donor works better, and almost everyone has a spare. As techniques improve for removing healthy kidneys and for suppressing the body's tendency to reject a transplant, doctors increasingly turn to kidneys from living donors, usually relatives. Last year, 43% of kidneys transplanted in the U.S. came from living donors, up from 28% a decade ago. But a biological barrier often blocks a transplant from a relative. In about a third of all would-be pairs, blood types are incompatible. In others, the sick person has antibodies that can initiate a rejection of the donated organ. It's heartbreaking "to have the treasure of the live donor and then have that not go forward because of a biological obstacle," says Massachusetts General Hospital transplant surgeon Francis DelMonico.

Occasionally, transplant centers spot a way out: One New England father with blood type A couldn't donate a kidney to his daughter with blood type B. So he gave a kidney to a teenager with blood type A, and the teenager's sister gave a kidney for the man's daughter. New England's transplant centers have done six such exchanges. Baltimore's Johns Hopkins University has done seven.

The crucial thing about Roth's work, from an economic point of view, is that it involves finding stable allocations using market-like situations without involving money. The kidney swaps in the New England situation are market-like, trading kidneys for kidneys in a way that makes all parties better-off, but they don't actually require kidneys to be bought and sold.

We can see the importance of this by looking at another paper of Roth's, not cited by the committee, on repugnance in markets (pdf). Roth demonstrates that some markets are limited because the very existance of a market in some goods is considered repugnant. He argues, for instance, that the trade in horse meat being banned in California is not done through fears that eating horse meat is unsafe; nor is it done for animal welfare reasons, since it is still legal to farm and kill horses. But banned it is, and Roth argues that the natural response of economists to situations of this type - to argue for freer markets - is wrong, since it ignores the very strong feelings involved in the situation. Instead:

Being aware of the sources of repugnance can only help make such discussions more productive, not least because it can help separate the issues that are fundamentally empirical—like the degree of crowding out of altruistic donations that might result from different incentive schemes compared to how much new supply might be produced—from areas of disagreement that are not primarily empirical.

Hopefully his new Nobel Prize should give that argument greater weight in the years ahead.

A patient receives a kidney in Johns Hopkins university in Baltimore. Photograph: Getty Images

Alex Hern is a technology reporter for the Guardian. He was formerly staff writer at the New Statesman. You should follow Alex on Twitter.

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“I felt very lonely”: addressing the untold story of isolation among young mothers

With one in five young mothers lonely “all the time”, it’s time for employers and services to step up.

“Despite having my child with me all the time, I felt very lonely,” says Laura Davies. A member of an advisory panel for the Young Women’s Trust, she had her son age 20. Now, with a new report suggesting that one in five young mums “feels lonely all the time”, she’s sharing her story.

Polling commissioned by the Young Women’s Trust has highlighted the isolation that young motherhood can bring. Of course, getting out and about the same as you did before is never easy once there’s a young child in the picture. For young mothers, however, the situation can be particularly difficult.

According to the report, over a quarter of young mothers leave the house just once a week or less, with some leaving just once a month.

Aside from all the usual challenges – like wrestling a colicky infant into their jacket, or pumping milk for the trip with one hand while making sure no-one is crawling into anything dangerous with the other – young mothers are more likely to suffer from a lack of support network, or to lack the confidence to approach mother-baby groups and other organisations designed to help. In fact, some 68 per cent of young mothers said they had felt unwelcome in a parent and toddler group.

Davies paints what research suggests is a common picture.

“Motherhood had alienated me from my past. While all my friends were off forging a future for themselves, I was under a mountain of baby clothes trying to navigate my new life. Our schedules were different and it became hard to find the time.”

“No one ever tells you that when you have a child you will feel an overwhelming sense of love that you cannot describe, but also an overwhelming sense of loneliness when you realise that your life won’t be the same again.

More than half of 16 to 24-year-olds surveyed said that they felt lonelier since becoming a mother, with more than two-thirds saying they had fewer friends than before. Yet making new friends can be hard, too, especially given the judgement young mothers can face. In fact, 73 per cent of young mothers polled said they’d experienced rudeness or unpleasant behaviour when out with their children in public.

As Davies puts it, “Trying to find mum friends when your self-confidence is at rock bottom is daunting. I found it easier to reach out for support online than meet people face to face. Knowing they couldn’t judge me on my age gave me comfort.”

While online support can help, however, loneliness can still become a problem without friends to visit or a workplace to go to. Many young mothers said they would be pleased to go back to work – and would prefer to earn money rather than rely on benefits. After all, typing some invoices, or getting back on the tills, doesn’t just mean a paycheck – it’s also a change to speak to someone old enough to understand the words “type”, “invoice” and “till”.

As Young Women’s Trust chief executive Dr Carole Easton explains, “More support is needed for young mothers who want to work. This could include mentoring to help ease women’s move back into education or employment.”

But mothers going back to work don’t only have to grapple with childcare arrangements, time management and their own self-confidence – they also have to negotiate with employers. Although the 2003 Employment Act introduced the right for parents of young children to apply to work flexibly, there is no obligation for their employer to agree. (Even though 83 per cent of women surveyed by the Young Women’s Trust said flexible hours would help them find secure work, 26 per cent said they had had a request turned down.)

Dr Easton concludes: “The report recommends access to affordable childcare, better support for young women at job centres and advertising jobs on a flexible, part-time or job share basis by default.”

Stephanie Boland is digital assistant at the New Statesman. She tweets at @stephanieboland