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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We're racing towards another private debt crisis - so why did no one see it coming?

The Office for Budget Responsibility failed to foresee the rise in household debt. 

This is a call for a public inquiry on the current situation regarding private debt.

For almost a decade now, since 2007, we have been living a lie. And that lie is preparing to wreak havoc on our economy. If we do not create some kind of impartial forum to discuss what is actually happening, the results might well prove disastrous. 

The lie I am referring to is the idea that the financial crisis of 2008, and subsequent “Great Recession,” were caused by profligate government spending and subsequent public debt. The exact opposite is in fact the case. The crash happened because of dangerously high levels of private debt (a mortgage crisis specifically). And - this is the part we are not supposed to talk about—there is an inverse relation between public and private debt levels.

If the public sector reduces its debt, overall private sector debt goes up. That's what happened in the years leading up to 2008. Now austerity is making it happening again. And if we don't do something about it, the results will, inevitably, be another catastrophe.

The winners and losers of debt

These graphs show the relationship between public and private debt. They are both forecasts from the Office for Budget Responsibility, produced in 2015 and 2017. 

This is what the OBR was projecting what would happen around now back in 2015:

This year the OBR completely changed its forecast. This is how it now projects things are likely to turn out:

First, notice how both diagrams are symmetrical. What happens on top (that part of the economy that is in surplus) precisely mirrors what happens in the bottom (that part of the economy that is in deficit). This is called an “accounting identity.”

As in any ledger sheet, credits and debits have to match. The easiest way to understand this is to imagine there are just two actors, government, and the private sector. If the government borrows £100, and spends it, then the government has a debt of £100. But by spending, it has injected £100 more pounds into the private economy. In other words, -£100 for the government, +£100 for everyone else in the diagram. 

Similarly, if the government taxes someone for £100 , then the government is £100 richer but there’s £100 subtracted from the private economy (+£100 for government, -£100 for everybody else on the diagram).

So what implications does this kind of bookkeeping have for the overall economy? It means that if the government goes into surplus, then everyone else has to go into debt.

We tend to think of money as if it is a bunch of poker chips already lying around, but that’s not how it really works. Money has to be created. And money is created when banks make loans. Either the government borrows money and injects it into the economy, or private citizens borrow money from banks. Those banks don’t take the money from people’s savings or anywhere else, they just make it up. Anyone can write an IOU. But only banks are allowed to issue IOUs that the government will accept in payment for taxes. (In other words, there actually is a magic money tree. But only banks are allowed to use it.)

There are other factors. The UK has a huge trade deficit (blue), and that means the government (yellow) also has to run a deficit (print money, or more accurately, get banks to do it) to inject into the economy to pay for all those Chinese trainers, American iPads, and German cars. The total amount of money can also fluctuate. But the real point here is, the less the government is in debt, the more everyone else must be. Austerity measures will necessarily lead to rising levels of private debt. And this is exactly what has happened.

Now, if this seems to have very little to do with the way politicians talk about such matters, there's a simple reason: most politicians don’t actually know any of this. A recent survey showed 90 per cent of MPs don't even understand where money comes from (they think it's issued by the Royal Mint). In reality, debt is money. If no one owed anyone anything at all there would be no money and the economy would grind to a halt.

But of course debt has to be owed to someone. These charts show who owes what to whom.

The crisis in private debt

Bearing all this in mind, let's look at those diagrams again - keeping our eye particularly on the dark blue that represents household debt. In the first, 2015 version, the OBR duly noted that there was a substantial build-up of household debt in the years leading up to the crash of 2008. This is significant because it was the first time in British history that total household debts were higher than total household savings, and therefore the household sector itself was in deficit territory. (Corporations, at the same time, were raking in enormous profits.) But it also predicted this wouldn't happen again.

True, the OBR observed, austerity and the reduction of government deficits meant private debt levels would have to go up. However, the OBR economists insisted this wouldn't be a problem because the burden would fall not on households but on corporations. Business-friendly Tory policies would, they insisted, inspire a boom in corporate expansion, which would mean frenzied corporate borrowing (that huge red bulge below the line in the first diagram, which was supposed to eventually replace government deficits entirely). Ordinary households would have little or nothing to worry about.

This was total fantasy. No such frenzied boom took place.

In the second diagram, two years later, the OBR is forced to acknowledge this. Corporations are just raking in the profits and sitting on them. The household sector, on the other hand, is a rolling catastrophe. Austerity has meant falling wages, less government spending on social services (or anything else), and higher de facto taxes. This puts the squeeze on household budgets and people are forced to borrow. As a result, not only are households in overall deficit for the second time in British history, the situation is actually worse than it was in the years leading up to 2008.

And remember: it was a mortgage crisis that set off the 2008 crash, which almost destroyed the world economy and plunged millions into penury. Not a crisis in public debt. A crisis in private debt.

An inquiry

In 2015, around the time the original OBR predictions came out, I wrote an essay in the Guardian predicting that austerity and budget-balancing would create a disastrous crisis in private debt. Now it's so clearly, unmistakably, happening that even the OBR cannot deny it.

I believe the time has come for there be a public investigation - a formal public inquiry, in fact - into how this could be allowed to happen. After the 2008 crash, at least the economists in Treasury and the Bank of England could plausibly claim they hadn't completely understood the relation between private debt and financial instability. Now they simply have no excuse.

What on earth is an institution called the “Office for Budget Responsibility” credulously imagining corporate borrowing binges in order to suggest the government will balance the budget to no ill effects? How responsible is that? Even the second chart is extremely odd. Up to 2017, the top and bottom of the diagram are exact mirrors of one another, as they ought to be. However, in the projected future after 2017, the section below the line is much smaller than the section above, apparently seriously understating the amount both of future government, and future private, debt. In other words, the numbers don't add up.

The OBR told the New Statesman ​that it was not aware of any errors in its 2015 forecast for corporate sector net lending, and that the forecast was based on the available data. It said the forecast for business investment has been revised down because of the uncertainty created by Brexit. 

Still, if the “Office of Budget Responsibility” was true to its name, it should be sounding off the alarm bells right about now. So far all we've got is one mention of private debt and a mild warning about the rise of personal debt from the Bank of England, which did not however connect the problem to austerity, and one fairly strong statement from a maverick columnist in the Daily Mail. Otherwise, silence. 

The only plausible explanation is that institutions like the Treasury, OBR, and to a degree as well the Bank of England can't, by definition, warn against the dangers of austerity, however alarming the situation, because they have been set up the way they have in order to justify austerity. It's important to emphasise that most professional economists have never supported Conservative policies in this regard. The policy was adopted because it was convenient to politicians; institutions were set up in order to support it; economists were hired in order to come up with arguments for austerity, rather than to judge whether it would be a good idea. At present, this situation has led us to the brink of disaster.

The last time there was a financial crash, the Queen famously asked: why was no one able to foresee this? We now have the tools. Perhaps the most important task for a public inquiry will be to finally ask: what is the real purpose of the institutions that are supposed to foresee such matters, to what degree have they been politicised, and what would it take to turn them back into institutions that can at least inform us if we're staring into the lights of an oncoming train?