There is no commonly accepted explanation for why European powers carved up the African continent in the 1880s. Most historians today discount economic explanations: by the 1880s African commodity exports were a sideshow. Rather, the explanations have to do with prestige-seeking by European governments combined with the fact that military imbalances made annexation easy. Related explanations add two sorts of security dilemma: (1) the fear that if one country did not annex an area another would; and (2) local political crises driving expansion as the easiest solution.
Now come Ewout Frankema (Wageningen University), Jeffrey Williamson (UW-Madison), and Pieter Woltje (Wageningen University) to show that African commodity prices enjoyed a sustained upturn between 1845 and 1885. Moreover, that upturn was stronger than for other regions.
This is pretty neat stuff, but as an explanation for colonialism it leaves a lot to be desired. No matter how you slice it, the profits from this trade were pretty small. In addition, we need to know how much of those profits were seized by Europeans even in the absence of formal control — my prior is that it would be a lot. Finally, we would need to know why the scramble waited until the 1880s: after all, the price rise started 40 years previously. (The authors partially address this with the point that French inland expansion started earlier.)
That said, these results do blow a hole in the Hopkins thesis that declining commodity prices caused intra-African wars over the remaining rents, thereby opening the door to European conquest. Neat stuff.