Food production should be able to keep up with the growth in world population that is projected to occur over the next 25 years, says population expert Tim Dyson.

• An important reason for this is that the worldwide growth in cereal yield shows no sign of slowing down, according to data from the UN Food and Agricultural Organization on cereal yields since 1951 (see figure).

• For example, in the United States the average cereal yield rose from 4.58 metric tons per hectare in 1989-91 to 5.04 metric tons per hectare in 1995-7.

• Some alarmists have pointed to a slowing of the percentage increase in agricultural productivity in recent years; but economists say because it is a linear trend it is inevitable that the annual percentage yield increase is declining.

• However, measured in absolute terms, which are what really matter, there is no real sign of any slackening in the growth of agricultural productivity.

Since 1945 the United States and Canada (with Australia) have been the world's most important exporters of cereals. The average growth of yields in these countries has been and remains strong.

Source: Tim Dyson (London School of Economics), "Prospects for feeding the world," British Medical Journal, October 9, 1999.

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For related BMJ articles on population http://www.bmj.com/cgi/content/full/319/7215/931