The two internal factors which routinely lead African pastoralists to exchange goods are the reproductive capacity of their capital goods and their specialization through the exploitation of areas unsuitable for agriculture. Livestock is a viable means of storing capital and labor, and can be exchanged for grain in times of shortage. Drought has the short term effect of causing stress sales of livestock; in the post-drought period when pastoralists are trying to rebuild their herds, demand outstrips supply and the prices rise. Livestock disease, government taxation and infrastructure impact the market system and pastoralists propensity to sell. In Kenya, overgrazing and livestock off-take rates are determined in part by the political agenda relating to land rights; increased off-take was encouraged as a means of cutting down on overgrazing, but implicit to this was the prioritization of settled cultivation over the growth of herds through pastoralism. For the pastoralists, sale is a rational move only where the return will be greater than simply eating or using the animal, so increased voluntary sales of livestock can be achieved by increasing the exchange value of livestock and livestock products in relation to their use value. The livestock industry in Nigeria is a large scale indigenous market structure; induced by cattle tax, the Fulani pastoralists market all the animals which were not needed for private consumption. The market is heavily dependent on interaction with non-Fulani livestock traders, and has responded to prices elsewhere in the economy, such as the 1980s oil boom. The market-system has been demand led, and shows the government acting in a positive way. In Niger, increased market orientation among the Fulani pastoralists is the result of seasonality of livestock sales, including the types and ages of animals sold, leading to changes in herd composition. In response to the market, herds have been diversified to include goats, sheep and camels as well as different breeds of cattle. One interpretation of the 1968-74 drought was to increase the number of livestock sales, and this, along with increased animal casualties, reduced the amount of available milk and increased dependence on cereal, and consequently on the market. However, after the drought, cereal production increased with herd size; herds characteristically had fewer lactating animals, and young were weaned earlier, resulting in larger herds and less milk. The upthrust of this would be that the pastoralists had found reason to diversify their output, rather than simply being driven to distress sales as the first interpretation would suggest. -- from Blench and Marriage Annotated Bibliography