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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Theresa May’s stage-managed election campaign keeps the public at bay

Jeremy Corbyn’s approach may be chaotic, but at least it’s more authentic.

The worst part about running an election campaign for a politician? Having to meet the general public. Those ordinary folk can be a tricky lot, with their lack of regard for being on-message, and their pesky real-life concerns.

But it looks like Theresa May has decided to avoid this inconvenience altogether during this snap general election campaign, as it turns out her visit to Leeds last night was so stage-managed that she barely had to face the public.

Accusations have been whizzing around online that at a campaign event at the Shine building in Leeds, the Prime Minister spoke to a room full of guests invited by the party, rather than local people or people who work in the building’s office space.

The Telegraph’s Chris Hope tweeted a picture of the room in which May was addressing her audience yesterday evening a little before 7pm. He pointed out that, being in Leeds, she was in “Labour territory”:

But a few locals who spied this picture online claimed that the audience did not look like who you’d expect to see congregated at Shine – a grade II-listed Victorian school that has been renovated into a community project housing office space and meeting rooms.

“Ask why she didn’t meet any of the people at the business who work in that beautiful building. Everyone there was an invite-only Tory,” tweeted Rik Kendell, a Leeds-based developer and designer who says he works in the Shine building. “She didn’t arrive until we’d all left for the day. Everyone in the building past 6pm was invite-only . . . They seemed to seek out the most clinical corner for their PR photos. Such a beautiful building to work in.”

Other tweeters also found the snapshot jarring:

Shine’s founders have pointed out that they didn’t host or invite Theresa May – rather the party hired out the space for a private event: “All visitors pay for meeting space in Shine and we do not seek out, bid for, or otherwise host any political parties,” wrote managing director Dawn O'Keefe. The guestlist was not down to Shine, but to the Tory party.

The audience consisted of journalists and around 150 Tory activists, according to the Guardian. This was instead of employees from the 16 offices housed in the building. I have asked the Conservative Party for clarification of who was in the audience and whether it was invite-only and am awaiting its response.

Jeremy Corbyn accused May of “hiding from the public”, and local Labour MP Richard Burgon commented that, “like a medieval monarch, she simply briefly relocated her travelling court of admirers to town and then moved on without so much as a nod to the people she considers to be her lowly subjects”.

But it doesn’t look like the Tories’ painstaking stage-management is a fool-proof plan. Having uniform audiences of the party faithful on the campaign trail seems to be confusing the Prime Minister somewhat. During a visit to a (rather sparsely populated) factory in Clay Cross, Derbyshire, yesterday, she appeared to forget where exactly on the campaign trail she was:

The management of Corbyn’s campaign has also resulted in gaffes – but for opposite reasons. A slightly more chaotic approach has led to him facing the wrong way, with his back to the cameras.

Corbyn’s blunder is born out of his instinct to address the crowd rather than the cameras – May’s problem is the other way round. Both, however, seem far more comfortable talking to the party faithful, even if they are venturing out of safe seat territory.

Anoosh Chakelian is senior writer at the New Statesman.

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