David McKenzie's blog
· Tim Ogden has two nice posts discussing critiques of randomized trials at the Financial Access Blog.
The past week has seen the World Bank building covered in banners and messages promoting the release of the 2012 World Development Report and the annual meetings. One of my colleagues drew my attention to this claim of impact on the sidewalk outside the Bank:
International migration is the most effective action that people in developing countries can take to increase their incomes and well-being. Yet our ability to learn about the policies that enhance or inhibit the gains to migration is severely restricted due to the poor state of migration data. One element of this is the lack of representative surveys of immigrants.
Last week I posted about a nice experiment that Lori Beaman and Jeremy Magruder had done to understand the role networks play in job-referrals.
When done well, randomized experiments at least provide internal validity – they tell us the average impact of a particular intervention in a particular location with a particular sample at a particular point in time. Of course we would then like to use these results to predict how the same intervention would work in other locations or with other groups or in other time periods.
- external validity
One of the frustrations facing job seekers worldwide, but especially in many developing countries, is how much finding a job depends on who you know rather than what you know. For example, in work I’ve done with small enterprises in Sri Lanka, less than 2 percent of employers openly advertised the position they last hired – with the most common ways of finding a worker being to ask friends, neighbors or family members for suggestions. Clearly networks matter for finding jobs.
One of the interesting discussions I had this last week was with a World Bank consultant trying to think about how to evaluate the impact of large-scale infrastructure projects. Forming a counterfactual is very difficult in many of these cases, and so the question is what one could think of doing. Since I get asked similar types of questions reasonably regularly, I thought I’d share my thoughts on this issue, and see whether anyone has good examples to share.
- evaluation methods
The latest issue of the Journal of Economic Perspectives (all content openly available online), has a symposium on the use of field experiments in economics. We’ve discussed or linked to posts on three of the four papers in previous blog posts: A paper on mechanism experiments by Ludwig, Kling and Mullainathan; a paper on the
- Research ethics
The New York Times political blog has just posted an interview between David Leonhardt and Sasha Issenberg about Issenberg’s forthcoming book on Presidential candidate Rick Perry’s campaign method. Notable is the use of randomized experiments in campaigning: