significance of maize as a staple varies across the continent. The highest amounts of maize consumed are found in Southern Africa at 85 kg/capita/year as compared to 27 in East Africa and 25 in West and Central Africa. In Lesotho, Malawi, South Africa, Zambia and Zimbabwe, average consumption is over 100 kg/capita/year. These amounts represent more than 50 percent of total calories in Lesotho, Malawi and Zambia, 43 percent in Zimbabwe, and 31 percent in South Africa.

As a point of comparison, the 2007 average of rice consumption in Southeast Asia as a whole is 131 kg/capita/year and rice represents 55 percent of total calories. Thus, for some countries in Sub-Saharan Africa, maize is important enough in farm production, incomes and diets that yield gains could have impacts on producer and consumer welfare similar to those that occurred with improved rice in Southeast Asia. However, food staples are much more diversified in many areas of Sub-Saharan Africa than they are in Asia (Larson et al., 2010).

# _Urbanization and Trade_

Net maize imports to Sub-Saharan Africa average around 1.5 M t or less than 5 percent of total consumption. Maize imports are generally small in West and Central Africa, but play an important role in Eastern and Southern Africa. Trade within the region, both formal and informal, is also significant in some years. However, many countries resort to discretionary and unpredictable trade policy controls such as import and export bans, as well as direct state trading operations, which have curtailed the potential of regional trade to reduce price instability (Chapoto and Jayne 2009).

Few countries in Sub-Saharan Africa are competitive in global markets for exports, largely because of high transport and logistics costs; for the same reasons, most countries are competitive for import substitution. Given both greater productivity and improved infrastructure, the expansion of regional markets could eventually provide the basis for competition in export markets (World Bank, 2009).

Within the next few decades, the majority of Sub-Saharan Africa‘s people will be living in urban centers and will depend on a diminishing minority of the population to produce food. Ongoing demographic change means that countries in eastern and southern Africa regions are increasingly dependent on imports of staple foods. Net maize exports in East and Southern Africa as regions display downward trends, with substantial variability, over the past few decades (FAOSTAT). Net exports are negligible in West and Central Africa and show no trend. All countries in Southern Africa have a negative trend in net maize exports. In East Africa, there is a negative trend in net maize exports for 2 of 6 countries (Kenya and Rwanda). Kenya and Zimbabwe, net exporters of maize in the 1970s and 1980s, are now chronic importers. Malawi has also been a net maize importer in four of the past six years. The reduction of maize production subsidies in South Africa has also reduced the exportable surplus in that country, although it remains a reliable exporter.

Urban populations are growing at over 4 percent per year in Sub-Saharan Africa compared to less than 1 percent among rural populations. To feed urban populations, especially in coastal cities, maize imports would have been much larger but for rising imports of wheat and rice. For example, in the urban areas of East and southern Africa shown in Table 3, wheat and rice (much of which is imported) are more important than maize in consumption. The consumption shares of wheat and rice in urban areas are growing rapidly even in areas where maize has long been the primary staple crop, reflecting the overall decline in maize self5