Perils of simulation: parallel streams and the case of stata's rnormal command
November 2012 - Large-scale simulation-based studies rely on at least three properties of pseudorandom number sequences: they behave in many ways like truly random numbers; they can be replicated; and they can be generated in parallel. There has been some divergence, however, between empirical techniques employing random numbers, and the standard battery of tests used to validate them. A random number generator that passes tests for any single stream of random numbers may fail the same tests when it is used to generate multiple streams in parallel. The lack of systematic testing of parallel streams leaves statistical software with important potential vulnerabilities. This paper shows one such vulnerability in Stata's rnormal function that went unnoticed for almost four years, and how to detect it. It then shows practical implications for the use of parallel streams in existing software.
Working Papaer 6278
Evaluating Workfare When the Work Is Unpleasant:Evidence for India’s National Rural Employment Guarantee Scheme
November 2012 - Prevailing practices in evaluating workfare programs have ignored the disutility of the type of work done, with theoretically ambiguous implications for the impacts on poverty. In the case of India's National Rural Employment Guarantee Scheme, past assessments have relied solely on household consumption per person as the measure of economic welfare.
Working Paper 6272
Handwashing Behavior Change at Scale: Evidence from a Randomized Evaluation in Vietnam
September 2012 - Handwashing with soap campaigns are de rigueur in developing countries, but little is known about their effectiveness. This paper evaluates a large-scale handwashing campaign in three provinces of Vietnam in 2010. Exposure to the campaign resulted in a slight increase in the availability of handwashing materials in the household, and caregivers in the treatment group were more likely to report washing hands at some of the times emphasized by the campaign. However, no differences were found between the treatment and control groups in actual handwashing with soap, the average level of which remains very low.
Working Paper 6207
Women’s Access to Labor Market Opportunities, Control of Household Resources, and Domestic Violence
July 2012 - While there are many positive societal implications of increased female labor force opportunities, some theoretical models and empirical evidence suggest that working can increase a woman's risk of suffering domestic violence. Using a dataset collected in peri-urban Dhaka, this analysis documents a positive correlation between work and domestic violence. This correlation is only present among women with less education or who were younger at first marriage. These results are consistent with a theoretical model in which a woman with low bargaining power can face increased risk of domestic violence upon entering the labor force as a husband seeks to counteract her increased bargaining power, while a woman with higher baseline bargaining power is protected from domestic violence because she can leave a violent marriage.
Working Paper 6149
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Owen Ozier. Microfranchising in Nairobi hits the BBC
November 2012 - This week, the BBC and the International Rescue Committee blog both featured a project that I am evaluating together with coauthors Maddalena Honorati and Pamela Jakiela. IRC approached us because they were interested in conducting a rigorous impact evaluation of their project.
Adam Wagstaff. When the snow fell on health systems research: a symposium sketch
November 2012 - It was the perfect finale. In the vast high-tech auditorium of Beijing's International Convention Center, the audience jostled in the queue to pose questions to the final plenary panel of the Second Global Symposium on Health Systems Research.
Adam Wagstaff. How can health systems “systematic reviews” actually become systematic?
October 2012 - In my post “Should you trust a medical journal?” I think I might have been a bit unfair. Not on The Lancet, which I have since discovered, via comments on David Roodman’s blog, has something of a track record of publishing sensational but not exactly evidence-based social science articles, but rather on Ernst Spaan et al. for challenging the systematicness of their systematic review of health insurance impacts in developing countries.
Shanta Devarajan and Jishnu Das. Improving access to drugs: Fitting the solution to the problem
October 2012 - Patricio Marquez’s post correctly identifies lack of access to quality medicines as one of the constraints to poor people’s health in Africa. But the solutions he recommends—more public money for “essential drugs benefits”, building resilient institutions, and providing physicians with better scientific information and guidelines about drug prescriptions—are unlikely by themselves to improve poor people’s health outcomes.
Adam Wagstaff. Who’s writing what in the ‘Knowledge Bank’? And is it being used?
October 2012 - An organization with ‘motor company’ in its name might produce several types of vehicle (cars, trucks, etc.) in several variations (models) at several different plants, and might sell these vehicles in several different regions of the world. The company wouldn’t last long if it didn’t know how many of each model – and at what cost – it was producing in each plant, and how many – and at what price – it was selling in each region. In the World Bank – where we like to think of ourselves as the ‘knowledge bank’ – we produce several types of document in several vice presidencies (VPUs) and we make them available in hard copy and in electronic format in all regions of the world.
Adam Wagstaff. Should you trust a medical journal?
September 2012 - While we non-physicians may feel a bit peeved when we hear “Trust me, I’m a doctor”, our medical friends do seem to have evidence on their side. GfK, apparently one of the world’s leading market research companies, have developed a GfK Trust Index, and yes they found that doctors are one of the most trusted professions, behind postal workers, teachers and the fire service. World Bank managers might like to know that bankers and (top) managers come close to the bottom, just above advertising professionals and politicians.
Previous Blogs & Research Briefs
Chiburis, R. C., J. Das, et al. (2012). "A practical comparison of the bivariate probit and linear IV estimators." Economics Letters 117(3): 762-766.
This paper compares asymptotic and finite sample properties of linear IV and bivariate probit in models with an endogenous binary treatment and binary outcome. The results provide guidance on the choice of model specification and help to explain large differences in the estimates depending on the specification chosen...
Filmer, D. and K. Scott (2012). "Assessing asset indices." Demography 49(1): 359-392.
The use of asset indices in welfare analysis and poverty targeting is increasing, especially in cases in which data on expenditures are unavailable or hard to collect. We compare alternative approaches to welfare measurement. Our analysis shows that inferences about inequalities in education, health care use, fertility, and child mortality, as well as labor market outcomes, are quite robust to the economic status measure used. Different measures—most significantly per capita expenditures versus the class of asset indices—do not, however, yield identical household rankings. Two factors stand out in predicting the degree of congruence in rankings. First is the extent to which expenditures can be explained by observed household and community characteristics...
Das, J., R. K. Das, et al. (2012). "The mental health gender-gap in urban India: Patterns and narratives." Social Science & Medicine 75(9): 1660–1672.
Women report significantly higher levels of mental distress than men in community studies around the world. We provide further evidence on the origins of this mental health gender-gap using data from 789 adults, primarily spousal pairs, from 300 families in Delhi, India. These data were collected between 2001 and 2003. We first confirm that, like in other studies, women report higher levels of mental distress and that gender differences in education, household expenditures and age do not explain the mental health gender-gap. In contrast, women report significantly higher levels of distress than men in families with adverse reproductive outcomes, particularly the death of a child...
Kazianga, H., D. de Walque, et al. (2012). "Educational and Child Labour Impacts of Two Food for Education Schemes: Evidence from a Randomized Trial in Rural Burkina Faso." Journal of African Economies 21(5): 723–760.
This paper uses a prospective randomised trial to assess the impact of two food-for-education schemes on education and child labour outcomes for children from low-income households in northern rural Burkina Faso. The two food-for-education programmes under consideration are, on the one hand, school meals where students are provided with lunch each school day, and, on the other hand, take-home rations which provide girls with 10 kg of cereal flour each month, conditional on 90% attendance rate. After the programme ran for one academic year, both programmes increased enrolment by 3–5 percentage points. The scores on mathematics improved for girls in both school meals and take-home rations villages...
Previous Journal Articles
The Elderly and Old Age Support in Rural China. Directions in Development Series
March 2012 - The Elderly and Old Age Support in Rural China examines projected demographic changes that will affect the economic well-being of China’s rural elderly over the next 20 years, taking into account both China’s sharp demographic transition and the continued migration of young adults to cities. The projected old age dependency ratio of 34 percent in China’s rural areas by 2030 suggests that support of the elderly is likely to be an increasing burden on China’s families.
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Health Equity and Financial Protection: Streamlined Analysis with ADePT Software
May 2011 - ADePT Health is a free-standing computer program that allows users to produce quickly - and with the minimal risk of errors - most tables that have become standard in applied health and equity analysis. ADePT produces summary statistics and charts that allow inequalities to be compared across countries and over time. This manual explains the methods ADePT uses, how to prepare data for it, how to navigate the ADePT interface to generate the desired tables and charts, and how to interpret them.
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Making Schools Work: New Evidence on Accountability Reforms
February 2011 - This book is about the threats to education quality in the developing world that cannot be explained by lack of resources. It reviews the observed phenomenon of service delivery failures in public education: cases where programs and policies increase the inputs to education but do not produce effective services where it counts – in schools and classrooms. It documents what we know about the extent and costs of such failures across low and middle-income countries. And it further develops the conceptual model posited in the World Development Report 2004: that a root cause of low-quality and inequitable public services – not only in education—is the weak accountability of providers to both their supervisors and clients.
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No small matter: the impact of poverty, shocks, and human capital investments in early childhood development
February 2011 - Education is often seen as a fundamental means to improve economic prospects for individuals from low income settings. However, even with increased emphasis on basic education for all, many individuals fail to achieve basic skills to succeed in life. The book presents evidence that one core reason is that by the time a child is old enough to attend school, there is already a wide disparity in cognitive skills and in emotional and behavioral development among children from households of different socioeconomic backgrounds. Low levels of cognitive development in early childhood strongly correlate with low socio-economic status (as measured by wealth and parental education) as well as malnutrition. These disadvantages are often exacerbated by economic crises.
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