In many household surveys, geographically clustered households report unit values of foods, which when corrected for quality effects and for measurement error, indicate the underlying spatial variation in prices, and can be matched to variation in demand patterns so as to estimate price elasticities. A 1979 household survey from the Côte d'Ivoire is used to estimate price elasticities for beef, meat, fish, cereals, and starches.

We investigate nutrition and expenditure in rural Maharashtra in India. We estimate that the elasticity of calorie consumption with respect to total expenditure is 0.3-0.5, a range that is in accord with conventional wisdom. The elasticity declines only slowly with levels of living and is far from the value of zero suggested by a recent revisionist literature. In these Indian data, the calories necessary for a day's activity cost less than 5 percent of the daily wage, which makes it implausible that income is constrained by nutrition rather than the other way around.

By buying cheap and selling dear, risk-neutral commodity speculators can smooth commodity prices and induce serial dependence in price even when none would exist under a simple process of supply and demand. Commodity prices are variable and strongly positively correlated from one year to the next. The variability is often explained by supply factors, and the autocorrelation by the activities of speculators. We show that this explanation is not consistent with the evidence. Speculation can substantially increase autocorrelation for prices that are weakly autocorrelated in its absence, but not to the high levels that are observed in the data.

The permanent income hypothesis implies that, for any cohort of people born at the same time, inequality in both consumption and income should grow with age. We investigate this prediction using cohort data constructed from 11 years of household survey data from the United States, 22 years from Great Britain, and 14 years from Taiwan. The data show that within-cohort consumption and income inequality measures do indeed increase with age in the three economies and that the rate of increase is similar in all three. According to the permanent income hypothesis, the increase in inequality reflects cumulative differences in the effects of luck on consumption. Other models of intertemporal choice--such as those with strong precautionary motives or liquidity constraints--can limit or even prevent the spread of inequality, as can insurance arrangements that share risk across individuals. The evidence on the spread of inequality can therefore be used to help quantify the extent to which private and social arrangements moderate the impact of risk on the distribution of individual welfare.

There is currently much debate about the effectiveness of foreign aid and about what kind of projects can engender economic development. There is skepticism about the ability of econometric analysis to resolve these issues or of development agencies to learn from their own experience. In response, there is increasing use in development economics of randomized controlled trials (RCTs) to accumulate credible knowledge of what works, without overreliance on questionable theory or statistical methods. When RCTs are not possible, the proponents of these methods advocate quasi-randomization through instrumental variable (IV) techniques or natural experiments. I argue that many of these applications are unlikely to recover quantities that are useful for policy or understanding: two key issues are the misunderstanding of exogeneity and the handling of heterogeneity. I illustrate from the literature on aid and growth. Actual randomization faces similar problems as does quasi-randomization, notwithstanding rhetoric to the contrary. I argue that experiments have no special ability to produce more credible knowledge than other methods, and that actual experiments are frequently subject to practical problems that undermine any claims to statistical or epistemic superiority. I illustrate using prominent experiments in development and elsewhere. As with IV methods, RCT-based evaluation of projects, without guidance from an understanding of underlying mechanisms, is unlikely to lead to scientific progress in the understanding of economic development. I welcome recent trends in development experimentation away from the evaluation of projects and toward the evaluation of theoretical mechanisms. (JEL C21, F35, O19)

In this essay, I review Robert Fogel's The Escape from Hunger and Premature Death, 1700–2100, which is concerned with the past, present, and future of human health. Fogel's work places great emphasis on nutrition, not only for the history of health, but for explaining aspects of current health, not only in comparing poor and rich countries, but in thinking about rich countries now and in the future. I discuss Fogel's analysis alongside alternative interpretations that place greater emphasis on the historical role of public health, and on the current and future role of improvements in medical technology.

I discuss mechanisms linking health and inequality and review evidence for effects of income inequality on aggregate and individual mortality, over time and over space. I conclude that there is no direct link. Correlations come from factors other than income inequality itself, some of which are linked to broader notions of inequality and inequity that are most likely important for health. Whether income redistribution can improve population health does not depend on the existence of a direct link between income inequality and health and remains an open question.