Angus Deaton of Princeton University wins the Nobel prize. Working with the World Bank, Deaton has played a huge role in expanding data in developing countries. When you read that world poverty has fallen below 10% for the first time ever and you want to know how we know— the answer is Deaton’s work on household surveys, data collection and welfare measurement. I see Deaton’s major contribution as understanding and measuring world poverty.

Measuring welfare sounds simple but doing it right isn’t easy. How do you compare the standard of living in two different countries? Suppose you simply convert incomes using exchange rates. Sorry, that doesn’t work. Not all goods are traded so exchange rates tend to reflect the prices of tradable goods but a large share of consumption is on hard-to-trade services. The Balassa-Samuelson effect tells us that services will tend to be cheaper in poorer countries (I always get a haircut when in a poor country but I don’t expect to get a great deal on electronics). As a result, comparing standards of living using exchange rates will suggest that developing countries are poorer than they actually are. A second problem is the cheese problem. Americans consume a lot of cheese, the Chinese don’t. Is this because the Chinese are too poor to consume cheese or because tastes differ? How you answer this question makes a difference for understanding welfare. A third problem is the warring supermarkets problem. Two supermarkets each claim that they have the lowest prices and they are both right! How is this possible? Consumers at supermarket A buy more of what is cheap at A and less of what is expensive at A and vice-versa for B. Thus, it would cost more to buy the A basket at store B and it would also cost more to buy the B basket at store A! So which supermarket is better? Comparing standards of living across countries isn’t easy and then you want to make these comparisons consistently over time as well! Deaton, working especially with the World Bank, helped to construct price indices for all countries that measure goods and services and he showed how to use these to make theoretically appropriate comparisons of welfare. Deaton’s presidential address to the American Economic Association in 2010 covers many of these issues.

I see Deaton’s work on world poverty as a tour de force, he made advances in theory, he joined with others to take the theory to the field to make measurements and he used the measurements to draw attention to important issues in the world.

Earlier in his career, Deaton developed tools to bring theory to data on consumption. A key contributions is the Almost Ideal Demand System. We all know that demand curves slope down which means that a fall in the price of the good in question increases the quantity demanded but in fact economic theory says that the demand for good X depends not just on the price of good X but at least potentially on the prices of all other goods. If we want to estimate how a change in policy will influence people’s choices we need to allow demand curves to interact in potentially many ways but we still want to constrain those reactions according to economic theory. In addition, economic theory tells us that an individual’s demand curve slopes down but it doesn’t necessarily imply that the aggregation of individual demand curves must slope down. Aggregation is tricky! The Almost Ideal Demand system, due initially to Deaton and Muellbauer, in 1980 and further developed since then shows how we can estimate demand systems on aggregates of consumers while still preserving and testing the constraints of economic theory.

The study of consumption leads naturally to the study of savings, consumption in future periods. Here we have Keynes’s famous propensity to consume theory (consumption is a fraction of current income), Milton Friedman’s permanent income hypothesis (consumption is a fraction of estimated lifetime income), Modigliani’s Life Cycle Hypothesis (borrow young, save when middle aged, dissave when old). Robert Hall, building on the work of Ramsey, showed in the 1970s that rational expectations implies the famous Euler equation that bedevils graduate students, which shows that suitably discounted changes in marginal utilities should follow a random walk. Deaton played a big role in testing the new theories, mostly finding them wanting.

Deaton’s book, The Great Escape, on growth, health and inequality is accessible and a good read. A controversial aspect of this work is that Deaton falls squarely into the Easterly camp (Deaton’s review of Tyranny of Experts is here) in thinking that foreign aid has probably done more harm than good.

Here is Deaton on foreign aid:

Unfortunately, the world’s rich countries currently are making things worse. Foreign aid – transfers from rich countries to poor countries – has much to its credit, particularly in terms of health care, with many people alive today who would otherwise be dead. But foreign aid also undermines the development of local state capacity. This is most obvious in countries – mostly in Africa – where the government receives aid directly and aid flows are large relative to fiscal expenditure (often more than half the total). Such governments need no contract with their citizens, no parliament, and no tax-collection system. If they are accountable to anyone, it is to the donors; but even this fails in practice, because the donors, under pressure from their own citizens (who rightly want to help the poor), need to disburse money just as much as poor-country governments need to receive it, if not more so. What about bypassing governments and giving aid directly to the poor? Certainly, the immediate effects are likely to be better, especially in countries where little government-to-government aid actually reaches the poor. And it would take an astonishingly small sum of money – about 15 US cents a day from each adult in the rich world – to bring everyone up to at least the destitution line of a dollar a day. Yet this is no solution. Poor people need government to lead better lives; taking government out of the loop might improve things in the short run, but it would leave unsolved the underlying problem. Poor countries cannot forever have their health services run from abroad. Aid undermines what poor people need most: an effective government that works with them for today and tomorrow. One thing that we can do is to agitate for our own governments to stop doing those things that make it harder for poor countries to stop being poor. Reducing aid is one, but so is limiting the arms trade, improving rich-country trade and subsidy policies, providing technical advice that is not tied to aid, and developing better drugs for diseases that do not affect rich people. We cannot help the poor by making their already-weak governments even weaker.

Here is Tyler’s post on Deaton.

Addendum: Chris Blattman offers a very good perspective and appreciation.