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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Cabinet audit: what does the appointment of Andrea Leadsom as Environment Secretary mean for policy?

The political and policy-based implications of the new Secretary of State for Environment, Food and Rural Affairs.

A little over a week into Andrea Leadsom’s new role as Secretary of State for Environment, Food and Rural Affairs (Defra), and senior industry figures are already questioning her credentials. A growing list of campaigners have called for her resignation, and even the Cabinet Office implied that her department's responsibilities will be downgraded.

So far, so bad.

The appointment would appear to be something of a consolation prize, coming just days after Leadsom pulled out of the Conservative leadership race and allowed Theresa May to enter No 10 unopposed.

Yet while Leadsom may have been able to twist the truth on her CV in the City, no amount of tampering will improve the agriculture-related side to her record: one barely exists. In fact, recent statements made on the subject have only added to her reputation for vacuous opinion: “It would make so much more sense if those with the big fields do the sheep, and those with the hill farms do the butterflies,” she told an audience assembled for a referendum debate. No matter the livelihoods of thousands of the UK’s hilltop sheep farmers, then? No need for butterflies outside of national parks?

Normally such a lack of experience is unsurprising. The department has gained a reputation as something of a ministerial backwater; a useful place to send problematic colleagues for some sobering time-out.

But these are not normal times.

As Brexit negotiations unfold, Defra will be central to establishing new, domestic policies for UK food and farming; sectors worth around £108bn to the economy and responsible for employing one in eight of the population.

In this context, Leadsom’s appointment seems, at best, a misguided attempt to make the architects of Brexit either live up to their promises or be seen to fail in the attempt.

At worst, May might actually think she is a good fit for the job. Leadsom’s one, water-tight credential – her commitment to opposing restraints on industry – certainly has its upsides for a Prime Minister in need of an alternative to the EU’s Common Agricultural Policy (CAP); a policy responsible for around 40 per cent the entire EU budget.

Why not leave such a daunting task in the hands of someone with an instinct for “abolishing” subsidies  thus freeing up money to spend elsewhere?

As with most things to do with the EU, CAP has some major cons and some equally compelling pros. Take the fact that 80 per cent of CAP aid is paid out to the richest 25 per cent of farmers (most of whom are either landed gentry or vast, industrialised, mega-farmers). But then offset this against the provision of vital lifelines for some of the UK’s most conscientious, local and insecure of food producers.

The NFU told the New Statesman that there are many issues in need of urgent attention; from an improved Basic Payment Scheme, to guarantees for agri-environment funding, and a commitment to the 25-year TB eradication strategy. But that they also hope, above all, “that Mrs Leadsom will champion British food and farming. Our industry has a great story to tell”.

The construction of a new domestic agricultural policy is a once-in-a-generation opportunity for Britain to truly decide where its priorities for food and environment lie, as well as to which kind of farmers (as well as which countries) it wants to delegate their delivery.

In the context of so much uncertainty and such great opportunity, Leadsom has a tough job ahead of her. And no amount of “speaking as a mother” will change that.

India Bourke is the New Statesman's editorial assistant.