I have a new working paper out at the AEHN series, this time on West Africa. It’s a long time in the making, mainly due to the huge amount of new data it contains, and it constitutes, to my knowledge, the first attempt to quantify the extent of market integration during the colonial period for any part of Africa between South Africa and the Sahara. What I find is considerable integration in grain markets — for rice and salt — over the colonial period, driven by infrastructure investment (intended largely, it should be said, to evacuate cash crops and move soldiers around, not to integrate non-traded staple grains between locations in West Africa.) But I also find an impact from precolonial states, particularly those of the Fulani jihads and of Samori Touré. Price correlations were higher among town pairs that were within these states compared to town pairs that were not.