I’m working on a major new project measuring market integration and food markets in tropical Africa and Southeast Asian in the colonial period, and in particular on the integration of grain and salt markets in French West Africa. Though a great deal has been written both about railways and their impact on the one hand and local trade on the other, there is still a lot of historiographical blanks on the question of the impact of the construction of colonial railways on local product markets. One question I am trying to answer is: how geographically wide were grain markets in Africa? The best way to answer this is to study the behaviour of prices over time, and that’s why I’m gathering as many grain prices as I can, but one interesting metric of trade distance can be gained by exploiting published railway statistics. These will often give tonnage (how much stuff) and kilometric tonnage (how much stuff for what distance). Dividing kilometric tonnage by tonnage gives a measure of the average distance travelled by a ton of produce. Usually, published statistics in sources like the Bulletin mensuel de l’Agence économique de l’Afrique occidentale française give only the aggregate kilometric tonnage for all products, but fortunately, for a few months in 1923-4, we are given kilometric tonnage by product for a number of African railways. (I suspect there are more detailed product-level statistics in the archives, and that’s on my list for my next trip early next year).

As a glimpse, though, the published statistics produce an interesting hierarchy of goods—one that largely accords with what we might have guessed about the spatial nature of trade by product. Of course, lines were of differing lengths, so I’ve also calculated the average distance travelled as a percentage of the total length of the line. Maize, for example, seems to have been transported relatively short distances — 44 km on the Chemin de fer de la Côte d’Ivoire, between Abidjan and Bouaké, and 94km on the Central Dahomey line between Cotonou and Savé, especially compared with long-distance traded goods like salt—141km on average on the Central Dahomey and 252km on average on the Côte d’Ivoire line.

Railway line	Good	Average travelled	% of total line
Central Dahomey	Maize	94 km	36%
	Palm oil	72 km	23%
	Salt	141 km	54%
	Yams	200 km	77%
Côte d’Ivoire	Bananas	87 km	28%
	Kola nuts	129 km	41%
	Maize	44 km	14%
	Palm oil	50 km	16%
	Rice	197 km	62%
	Salt	252 km	80%
East Dahomey	Maize	41 km	51%
	Palm oil	21 km	26%
	Salt	25 km	31%
Kayes–Niger	Kola nuts	401 km	73%
	Millet	197 km	36%
	Rice	296 km	54%
	Salt	354.7 km	65%
	Shea butter	288 km	52%
	Heating wood	80 km	15%