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.

Photo: Getty
Show Hide image

Theresa May could live to regret not putting Article 50 to a vote sooner

Today's Morning Call.

Theresa May will reveal her plan to Parliament, Downing Street has confirmed. They will seek to amend Labour's motion on Article 50 adding a note of support for the principle of triggering Article 50 by March 2017, in a bid to flush out the diehard Remainers.

Has the PM retreated under heavy fire or pulled off a clever gambit to take the wind out of Labour's sails while keeping her Brexit deal close to her chest? 

Well, as ever, you pays your money and you makes your choice. "May forced to reveal Brexit plan to head off Tory revolt" is the Guardian's splash. "PM caves in on plans for Brexit" is the i's take. "May goes into battle for Brexit" is the Telegraph's, while Ukip's Pravda aka the Express goes for "MPs to vote on EU exit today".

Who's right? Well, it's a bit of both. That the government has only conceded to reveal "a plan" might mean further banalities on a par with the PM's one-liner yesterday that she was seeking a "red white and blue Brexit" ie a special British deal. And they've been aided by a rare error by Labour's new star signing Keir Starmer. Hindsight is 20:20, but if he'd demanded a full-blown white paper the government would be in a trickier spot now. 

But make no mistake: the PM didn't want to be here. It's worth noting that if she had submitted Article 50 to a parliamentary vote at the start of the parliamentary year, when Labour's frontbench was still cobbled together from scotch-tape and Paul Flynn and the only opposition MP seemed to be Nicky Morgan, she'd have passed it by now - or, better still for the Tory party, she'd be in possession of a perfect excuse to reestablish the Conservative majority in the House of Lords. May's caution made her PM while her more reckless colleagues detonated - but she may have cause to regret her caution over the coming months and years.

PANNICK! AT THE SUPREME COURT

David Pannick, Gina Miller's barrister, has told the Supreme Court that it would be "quite extraordinary" if the government's case were upheld, as it would mean ministers could use prerogative powers to reduce a swathe of rights without parliamentary appeal. The case hinges on the question of whether or not triggering Article 50 represents a loss of rights, something only the legislature can do.  Jane Croft has the details in the FT 

SOMETHING OF A GAMBLE

Ministers are contemplating doing a deal with Nicola Sturgeon that would allow her to hold a second independence referendum, but only after Brexit is completed, Lindsay McIntosh reports in the Times. The right to hold a referendum is a reserved power. 

A BURKISH MOVE

Angela Merkel told a cheering crowd at the CDU conference that, where possible, the full-face veil should be banned in Germany. Although the remarks are being widely reported in the British press as a "U-Turn", Merkel has previously said the face veil is incompatible with integration and has called from them to be banned "where possible". In a boost for the Chancellor, Merkel was re-elected as party chairman with 89.5 per cent of the vote. Stefan Wagstyl has the story in the FT.

SOMEWHERE A CLOCK IS TICKING

Michael Barnier, the EU's chief Brexit negotiator, has reminded the United Kingdom that they will have just 15 to 18 months to negotiate the terms of exit when Article 50 is triggered, as the remaining time will be needed for the deal to secure legislative appeal.

LEN'S LAST STAND?

Len McCluskey has quit as general secretary of Unite in order to run for a third term, triggering a power struggle with big consequences for the Labour party. Though he starts as the frontrunner, he is more vulnerable now than he was in 2013. I write on his chances and possible opposition here.

AND NOW FOR SOMETHING COMPLETELY DIFFERENT

Emad asks if One Night Stand provides the most compelling account of sex and relationships in video games yet.

MUST READS

Theresa May is becoming adept at avoiding defeats says George

Liv Constable-Maxwell on what the Supreme Court protesters want

Theresa May risks becoming an accidental Europe wrecker, says Rafael Behr

Get Morning Call in your inbox every weekday - sign up for free here.

Stephen Bush is special correspondent at the New Statesman. His daily briefing, Morning Call, provides a quick and essential guide to British politics.