世界経済・社会統計 = World development indicators

Output per worker varies enormously across countries. Why? On an accounting basis, our analysis shows that differences in physical capital and educational attainment can only partially explain the variation in output per worker--we find a large amount of variation in the level of the Solow residual across countries. At a deeper level, we document that the differences in capital accumulation, productivity, and therefore output per worker are driven by differences in institutions and government policies, which we call social infrastructure. We treat social infrastructure as endogenous, determined historically by location and other factors captured in part by language.

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Why Do Some Countries Produce so Much More Output Per Worker than Others

Does finance affect economic growth? A number of studies have identified a positive correlation between the level of development of a country's financial sector and the rate of growth of its per capita income. As has been noted elsewhere, the observed correlation does not necessarily imply a causal relationship. This paper examines whether financial development facilitates economic growth by scrutinizing one rationale for such a relationship; that financial development reduces the costs of external finance to firms. Specifically, we ask whether industrial sectors that are relatively more in need of external finance develop disproportionately faster in countries with more developed financial markets. We find this to be true in a large sample of countries over the 1980s. We show this result is unlikely to be driven by omitted variables, outliers, or reverse causality.

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Financial Dependence and Growth

Output per worker varies enormously across countries. Why? On an accounting basis our analysis shows that differences in physical capital and educational attainment can only partially explain the variation in output per worker—we find a large amount of variation in the level of the Solow residual across countries. At a deeper level, we document that the differences in capital accumulation, productivity, and therefore output per worker are driven by differences in institutions and government policies, which we call social infrastructure. We treat social infrastructure as endogenous, determined historically by location and other factors captured in part by language. In 1988 output per worker in the United States was more than 35 times higher than output per worker in Niger. In just over ten days the average worker in the United States produced as much as an average worker in Niger produced in an entire year. Explaining such vast differences in economic performance is one of the fundamental challenges of economics. Analysis based on an aggregate production function provides some insight into these differences, an approach taken by Mankiw, Romer, and Weil [1992] and Dougherty and Jorgenson [1996], among others. Differences among countries can be attributed to differences in human capital, physical capital, and productivity. Building on their analysis, our results suggest that differences in each element of the production function are important. In particular, however, our results emphasize the key role played by productivity. For example, consider the 35-fold difference in output per worker between the United States and Niger. Different capital intensities in the two countries contributed a factor of 1.5 to the income differences, while different levels of educational attainment contributed a factor of 3.1. The remaining difference—a factor of 7.7—remains as the productivity residual. * A previous version of this paper was circulated under the title ‘‘The Productivity of Nations.’’ This research was supported by the Center for Economic Policy Research at Stanford and by the National Science Foundation under grants SBR-9410039 (Hall) and SBR-9510916 (Jones) and is part of the National Bureau of Economic Research’s program on Economic Fluctuations and Growth. We thank Bobby Sinclair for excellent research assistance and colleagues too numerous to list for an outpouring of helpful commentary. Data used in the paper are available online from http://www.stanford.edu/,chadj.

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Why do Some Countries Produce So Much More Output Per Worker than Others

The present historical moment may seem a particularly inopportune time to review Bowling Alone, Robert Putnam's latest exploration of civic decline in America. After all, the outpouring of volunteerism, solidarity, patriotism, and self-sacrifice displayed by Americans in the wake of the September 11 terrorist attacks appears to fly in the face of Putnam's central argument: that \"social capital\" -defined as \"social networks and the norms of reciprocity and trustworthiness that arise from them\" (p. 19)'has declined to dangerously low levels in America over the last three decades. However, Putnam is not fazed in the least by the recent effusion of solidarity. Quite the contrary, he sees in it the potential to \"reverse what has been a 30to 40-year steady decline in most measures of connectedness or community.\"' As an example of how the current \"war on terrorism\" could generate a durable civic renewal, Putnam points to the burst in civic practices that occurred during and after World War II, which he says \"permanently marked\" the generation that lived through it and had a \"terrific effect on American public life over the last half-century.\" 3 If Americans can follow this example and channel their current civic

Bowling alone: The collapse and revival of American community

Acholuric jaundice in the adult

Advance Market Commitments

The human capital of young and old workers are imperfect substitutes both in production and in on-the-job training. This helps explain why capital does not flow from rich to poor countries, causing instantaneous convergence of per capita output. If each generation chooses its human capital optimally given that of the previous and succeeding generations, human capital follows a unique rational- expectations path. For moderate substitutability, human capital within each sector oscillates relative to that in other sectors, but aggregate human capital converges to the steady state monotonically, at rates consistent with those observed empirically.

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Young Workers, Old Workers, and Convergence

In this month’s issue, Liu and others present new evidence on the effects of deworming children from a clusterrandomized trial conducted in rural China. This was a useful, well-conducted study. The study found that a program in which school-age children were given deworming pills in school to take at home reduced infection prevalence modestly (end line prevalence of any worm infection was 31.4% in the control group and 27.7% in the treatment group). However, the authors could not reject the hypothesis that the program had no effect on nutrition, cognition, or school performance. As Liu and others emphasized, their results should be interpreted in light of the context they examined. The authors noted that in their setting, baseline prevalence of soil-transmitted helminths (STH) was low (31% for Ascaris, 23–24% for Trichuris, and 1% for hookworm), infections were “light intensity,” and even within the light-intensity group, measured egg counts were low. For example, mean infection intensity among children infected with Ascaris was less than 1,000 eggs per gram (epg; up to 4,999 epg is a light infection) and infection intensity for Trichuris was less than 70 epg (up to 1,000 epg is a light infection). The authors are to be commended for reporting prevalence and intensity for all three STH species, which greatly aids the interpretability of their results. Compliance with the deworming treatment was low, presumably because the study differed from most schoolbased deworming programs, and in particular from the standard World Health Organization (WHO) protocol; in accordance with Chinese regulations preventing children from taking the drugs at school, students were given pills to consume at home. Only 52% of participants reported taking all the recommended pills (75.6% reported taking at least half of the recommended dose of albendazole [200 mg] in both rounds of treatment). Compliance was self-reported, so any social desirability bias by respondents would mean that true compliance was lower than 52%. The fact that the end line difference in prevalence between the treatment and comparison group was only 3.7% points could potentially be explained by a combination of high rates of reinfection and this relatively low rate of compliance. It is useful to first consider the point estimates of effects in the Liu study and then consider issues of hypothesis testing and statistical power. The estimated effects in the Liu study were largely consistent with the results of a metaanalysis recently conducted by Croke and others on the impact of mass drug administration (MDA) on weight gain. The Croke analysis found that, in the environments where WHO recommends deworming, school-based MDA was effective in increasing weight, and indeed that it was very cost-effective relative to school feeding (school feeding was an example of a nutrition program that targeted similar populations for which, based on a review of randomizedcontrolled trials, the authors were able to identify a costeffectiveness analysis). Although too few studies have been conducted to draw strong conclusions about how effects vary with prevalence, point estimates are consistent with the commonsense view that effects are smaller in lower prevalence environments. Among studies in environments with greater than 50% infection prevalence in the Croke study, the average weight gain estimated in a random effects meta-analysis was 0.18 kg (95% confidence interval [CI] 0.07, 0.29). In contrast, the average effect in settings with less than 50% infection prevalence was 0.06 kg (95% CI −0.13, 0.25). A separate meta-analysis, by TaylorRobinson and others, also estimated an average weight gain of 0.06 kg in under 50% infection prevalence settings. In this lower prevalence sample, the Croke study estimated that the standard deviation of true effects was 0.25 kg. Using the method of Higgins and others, this implies that approximately 95% of places are expected to have a true effect in the range −0.59 to 0.71 kg. To put the outcomes in comparable terms, the weight gain estimate from the Liu study expressed in kilograms (rather than weight-for-age z score) was 0.03 (95% CI −0.25, 0.32). This clearly was well within the expected range. It is also unsurprising that the point estimates in the Liu study were lower than the estimated mean effects from this meta-analysis, since reported compliance was only 52% and infection prevalence at end line was only 12% lower in the treatment group. Although not consistently reported, compliance was typically 80–100% in other trials incorporated in the meta-analysis. Assuming that treatment effects were proportional to compliance and compliance was 0.52 implies that with full compliance, the estimated effect in the Liu study would have been (1/0.52) × 0.03 kg = 0.06 kg, close to the average estimated effect found by Croke and others in studies with less than 50% prevalence. Thus, while the results of the Liu study were consistent with the Croke analysis and with the hypothesis that MDA is cost-effective, the confidence intervals were wide enough to also encompass zero effect. The study was larger and better powered than many earlier trials, but as discussed later, power is inherently limited due to low prevalence and low compliance. Moreover, while the cluster-randomized nature of the trial was necessary to pick up potential epidemiological spillovers from treatment and thus to accurately measure impact, it did limit statistical power. Statistical power is limited in low-prevalence settings, since any effect on infected children will be averaged together with effects on uninfected children, who cannot benefit directly from treatment. The authors state that among the 10 outcomes of interest, STH prevalence was the outcome that *Address correspondence to Michael Kremer, Department of Economics, Harvard University, Littauer Center M-20, Cambridge MA, 02138. E-mail: mkremer@fas.harvard.edu

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More Evidence on the Effects of Deworming: What Lessons Can We Learn?

Proposals for education reform generally focus on teachers and curricula. But the most important factor in education may be the student himself or herself. A growing number of states, including Georgia, Michigan, New York, and Massachusetts, have established programs that provide financial rewards in the form of merit scholarships for college for students who perform well academically. However, such programs are controversial with some educators, and the structure of many existing programs in the United States makes it difficult to evaluate rigorously the impact of such incentive programs because it is hard to identify for comparison a credible group of students who were not eligible for the program. [ILLUSTRATION OMITTED] Examining the experiences of programs outside the United States may well be informative in helping to understand the impact of incentives for students. We collected evidence from a program in Kenya, in which girls in public schools who performed well were offered merit scholarships that covered the cost of the fees charged by public schools at the time. Their families were offered grants to help cover the cost of school supplies. The program was implemented by a nonprofit organization, which phased it into a number of schools in random order, allowing us to compare schools that were eligible for the program with other schools where the program had not yet been introduced. The results of our evaluation, conducted in 2001 and 2002, indicate that the program significantly improved the test scores of girls. Moreover, the program had salutary spillover effects: test scores of students who were not eligible for--or had no hope of earning--the award also improved, as did school attendance for both students and teachers. [ILLUSTRATION OMITTED] A Deficit of Data on Merit Scholarships Prior to our study, we had little information on the value of using scholarships as incentives to learn. One of the few existing sources of evidence in the United States is Georgia's HOPE (Helping Outstanding Pupils Educationally) scholarship program, which awards college scholarships to high school students who graduate with at least a B average and attend college in-state. After the program was introduced in 1993, the average SAT score for the Peach State's high school seniors rose almost 40 points. But since all students in the state were eligible, there was no way of determining, with a reliable degree of certainty, whether factors other than the scholarship had also contributed to the outcomes. Outside the United States, a randomized study among high school students in Israel conducted by economists Joshua Angrist of MIT and Victor Lavy of Hebrew University found that students eligible for cash awards for good performance were 6 to 8 percentage points more likely to pass their matriculation exams than other students in the same school. The opportunity to evaluate the Kenyan program has enabled us to address many of the problems of earlier research on merit scholarships. Because the schools participating in the Kenyan scholarship program were randomly selected, we could credibly identify its effects. We were also able to collect data on student and teacher attendance, purchases of school supplies, students' use of time, and a range of student attitudes about school that allowed us to explore the mechanisms by which merit scholarships affect schooling. Finally, as this same region in Kenya has been the site of randomized evaluations of several other education interventions, we can compare the cost-effectiveness of the scholarship program with alternative programs such as those that provide textbooks to students or performance-based incentives for teachers. Remarkably, we found little evidence to support the common criticisms of merit scholarships. The Kenyan program, for instance, did not appear to have led students to focus on test performance at the expense of other dimensions of learning. …

Michael Kremer

Papers

Acholuric jaundice in the adult

Advance Market Commitments

Young Workers, Old Workers, and Convergence

More Evidence on the Effects of Deworming: What Lessons Can We Learn?

Incentives to learn: merit scholarships that pay kids to do well