Friday, 9 December 2016

The debate over poached elephants

No, this isn't a post about the best method for cooking endangered species. Back in June, I wrote a post about this NBER Working Paper by Solomon Hsiang (UC Berkeley) and Nitin Sekar (Princeton). In the paper, Hsiang and Sekar demonstrated that a one-time legal sale of stockpiled ivory that happened in 2008 led to a significant increase in elephant poaching.

Since that working paper was released, there has been quite a debate over the validity of the results. First, Quy-Toan Do (World Bank), Andrei Levchenko (University of Michigan) and Lin Ma (National University of Singapore) wrote this blog post on the World Bank website, where they showed that Hsiang and Sekar's results were present only in a subsample of small sites (i.e. sites where there were few elephant carcasses). Do et al. concluded:
In this short discussion, we argued that the results reported by Hsiang and Sekar are confined to only the smallest sites surveyed by the MIKE programme. Aggregate poaching therefore did not experience a step increase in 2008 as argued by the authors. Our data on raw ivory prices in both Africa and China further support the conclusion that the 2008 one-off sale actually had no discernible effects on ivory markets. Rather, we postulate that small changes in the classification of carcasses could account for the results documented by Hsiang and Sekar.
Hsiang and Sekar then responded to the criticisms here, where they argue that the Do et al. results were the "result of a sequence of coding, inferential, and logical errors".

In the latest on this debate, Do et al. have responded to the response. In this latest response, they included all of the Stata code and links to the dataset, so that you can replicate their results and test alternative results:
Hsiang and Sekar's results are now looking increasingly shaky. We'll see if they have any further response (to the response to their response)...
[HT: David McKenzie at Development Impact]

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