reflected in regional average yields, which are as high as 1.7 in West Africa and 1.5 in East Africa, but only 1.1 in Southern Africa. From 1961-2008, area growth accounted for two-thirds of the overall 3 percent annual production growth in Sub-Saharan Africa; yield growth has averaged only 1 percent annually.

Growth rates vary considerably in each region of the continent and by decade (depending on endpoints chosen and the incidence of droughts), sometimes appearing negative but also much higher during episodes of success. In some cases, such as Zimbabwe and Zambia, trends in maize production have changed abruptly with policy shifts, and in other countries such as Angola and Mozambique, prolonged civil wars depress trends. The yield gap between countries in Sub-Saharan Africa and those with comparable production conditions is large, although it narrows if only rainfed areas are considered. It is important to recognize, however, that yield variability is much greater in Sub-Saharan Africa than elsewhere on a world scale (Box 1).

## **Box 1: How do yields in Sub-Saharan Africa compare to those of other tropical regions?**

Average yields and yield growth rates in other countries in tropical rainfed environments provide points of contrast. From 2005-2008, average maize yields were estimated at 3.8 t/ha in Brazil, 3.1 t/ha in Mexico, 2.5 t/ha in the Philippines, and 3.9 t/ha in Thailand, compared to 1.4 t/ha in Sub-Saharan Africa. Annual yield growth from 19612008 averaged 2.4 percent, 1.8 percent, 2.8 percent and 1.6 percent respectively in Brazil, India, Philippines and Thailand, on average about double the 1 percent growth in Sub-Saharan Africa. However, a careful analysis of subnational data, suggests that netting out irrigated area which is important in all but Brazil, the gap between yields in Africa and rainfed areas elsewhere is smaller although still sizeable. For example, rainfed maize yields in Mexico are just over 2 t/ha and have been rising at about 1.9 percent per annum since the 1970s. Much of this yield gap would be due to higher and more widely adopted fertilizer use on Mexican maize.

Maize yield variability is extremely high in sub-Saharan Africa. Even among developing countries that have approximately the same mean yields, the variability of yields is nearly always higher in countries of Sub-Saharan Africa (Byerlee and Heisey 1997). Countries in Southern Africa have the highest coefficients of variation (Table 2). Zimbabwe‘s coefficient of variation in maize production from 1991-2007 was 41 percent, as compared to 33 percent in Malawi, 31 percent in Zambia, and only 11 percent in Kenya. Climatic factors are responsible for much of yield variability, which as discussed later also aggravates price variability. By contrast, in countries where rice is major food staple in Asia, coefficients of variation in production are in the single digits.

# _Trends in Maize Consumption and Trade_

In high-income countries, an estimated 70 percent of maize is destined for feed, only 3 percent is consumed directly by humans, and the remainder is used for biofuels, industrial products and seed. In Sub-Saharan Africa outside of South Africa, 77 percent of maize is used as food and only 12 percent serves as feed.

Maize, predominantly white, is consumed in Sub-Saharan Africa boiled or cooked. The two types of white maize (dent and flint) are largely associated with different food products (FAO, 1997). Dent maize is soft and floury and used for porridges, while flint maize has a hard, vitreous endosperm and is used primarily for gruel or couscous. In parts of Sub-Saharan Africa such as Malawi, flint maize has been preferred to dent because of smaller losses incurred in traditional storage and processing practices.

Maize has accounted for 22 to 25 percent of starchy staple consumption in Africa from 1980, representing the largest single source of calories, followed closely by cassava.<sup>3</sup> The

> 3 By region, no trend is apparent in per capita maize consumption over the past five decades, although a slight increase is visible in Central Africa. However, in Ethiopia, maize as a percentage of daily energy has nearly doubled from 10 percent in 1961-63 to 19 percent in 2003-2005

4