First – a little bit of history on this. In 2012, myself and two very nice co-authors, Luca Marchiori and Jean-Francois Maystadt, published a paper entitled “The impact of weather anomalies on migration in sub-Saharan Africa” in the Journal of Environmental Economics and Management. Some time later, our paper (the previous working paper version, but not much different to the published one) was put under fire in another article (Lilleør and Van den Broeck 2011). This paper suggested that income variability was omitted in our work which would thus bias our results.

We were a little surprised about this, since only our paper was addressed along these lines while clearly any article in this line of literature should also have been criticised long these lines. These critics spiced us up, motivated us to get back to our original work and re-think it with the criticisms that we received in mind. And so that we did. And then we saw the same thought coming up in a first draft of the new IPCC report, page 21 (by the way – read the report it is a nice one).

And now, exclusively for the readers here, we have a new paper discussing whether it makes sense to introduce income variability into these migration frameworks, study its role, and see whether there is really an omitted variable bias in our work or not. Find out about all this and more,  HERE. Enjoy!


It was recently suggested that the role of environmentally-induced income variability as a determinant of migration has been studied little to none. We provide a theoretical discussion and an overview of the empirical literature on this. We also extend a previous empirical study of ours by including income variability. Our findings lead us to acknowledge that income variability is a negligible driver of migration decisions at the macroeconomic level.

UPDATE (25 July 2013): Michael Oppenheimer just contacted us (me and my co-authors) and let us know that in the second draft of the IPCC report the criticism is taken out. Let us note that the critics of Lilleør and Van den Broeck were not wrong ex ante. In my opinion they simply tried to point out that in a microeconomic study the variable income variability was found to be important, while no macroeconomic study had picked up on this.

But if one then thinks more carefully – like we hopefully did in our new working paper – about the reasons for which macroeconomic studies should use income variability (instead of, or in conjunction with, the income level) as a determinant of migration, then the case for income variability seems shaky at most…