Wednesday, January 16, 2008

Mosquito nets: Easterly vs. Sachs

Mark Thoma points to an entry in Dani Rodrik's blog that in the mosquito net battle, Sachs seems to have beaten Easterly. Virginia Postrel in the Washington Post review of "A White Man's Burden" explains:
It's not that simple, William Easterly argues in "The White Man's Burden." Take those mosquito nets. When aid agencies hand them out in poor countries, he writes, "nets are often diverted to the black market . . . or wind up being used as fishing nets or wedding veils." Free nets don't get to the people who need them.

This is the text of the blog entry:
On insecticide-treated bed nets (ITNs), at least. There has been an ongoing battle between Sachs and segments of the global public health community on ... whether ITNs should be distributed free (the Sachs position) or at a positive, albeit subsidized price. Those who favor the latter argue, in part, that charging a fee makes the program more sustainable and that it reduces wastage from giving away the nets to those who do not need or will not use it. See the arguments here (gated, unfortunately). ... A new randomized experiment carried out by Jessica Cohen and Pascaline Dupas reaches striking and unambiguous results:

Taken together, our results suggest that cost-sharing ITN programs may have difficulty reaching a large fraction of the populations most vulnerable to malaria. ...[W]e find that ... free distribution is more cost-effective than partial-but-still-highly subsidized distribution... We also find that ... the number of infant lives saved is highest when ITNs are distributed free. Finally, we do not find that free distribution generates higher leakage of ITNs to non-intended beneficiaries. To the contrary, we observed more leakage and theft (by clinic staff) when ITNs were sold at a higher price. We also did not observe any second-hand market develop in areas with free distribution.

This is randomized experiments at its best: it addresses an important policy question and significantly changes (or should change) our priors on it.

If the results are so unambiguous then why was there a debate in the first place? Perhaps it was an over reliance on anecdotal evidence such as that presented in Easterly's book illustrated in the passage above. If aid agencies had flooded countries with mosquito nets (thereby driving the price close to zero) would we have observed the behaviors documented in the book? The challenge now in advancing the results of the randomized study is to see how well it scales up. My take on the problem is one of access -- there may be a large proportion of the population that lives in hard to access areas. If this is the case, will it pass the cost-benefit test?

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