Men tend to produce crops for cash, or hire out their labour. The bulk of the work on food produced for family and local consumption falls to women. In sub-Saharan Africa, women grow and sell 80 to 90 per cent of this food. They produce 50 to 60 per cent of Asia's food, 46 per cent of the Caribbean's and more than 30 per cent of Latin America's. Furthermore, up to 80 per cent of all fish and shellfish caught by local, artisanal fisherfolk in tropical Africa, Asia and the Pacific are cleaned, dried, smoked and marketed by women and children. In poor families nutrition is largely the responsibility of women.

Most of this work is not included in national income accounts, yet most societies would fall apart without it. If women's work in and around the house were monetized, the International Labour Organization (ILO) reckons their collective contribution to the world economy would easily top $4 trillion a year. Their task has become more and more difficult. In a parallel process, family holdings have become smaller, while large holdings have grown. Small and subsistence farmers find themselves squeezed by lower prices, or forced off their land altogether.

This has given rise to another demographic trend: the exodus of men from rural areas to cities and towns where they seek wage employment. Although some of this migration is seasonal, with men returning for planting and harvesting, increasingly women find themselves the de facto heads of farm households for much of the year. On average, 35 per cent of all households in the Caribbean are headed by women, many of them single mothers with few if any skills and little education. The average for Latin America is 21 per cent; it is 22 per cent in sub-Saharan Africa and 18 per cent in Southeast Asia and Oceania. In some parts of West Africa up to 60 per cent of all households are headed by women, though most are formally married. In most developing regions, the percentage of women heads of household seems to be rising.

Lack of a male head of household may not translate into poorer family nutrition. Recent research on women-headed households has revealed markedly improved household diets, especially for children under five. In Rwanda, female-headed households consume 377 more calories per person per day when compared to male-headed households; in the Gambia, they add 322 more calories per day to family diets. Female-dominated households in Kenya have significantly lower incidences of diarrhoea among pre-schoolers than children from male-dominated households.

Part of this can be explained by the fact that women tend to devote more of the household income to food purchases. An intensive survey of 278 households in rural Nepal found that when both subsistence production and market production were considered, women, despite having two-thirds less cash income than men, still contributed 15 per cent more money to the monthly household budget. In general, men spent a disproportionate amount of income from cash crops or wages on relative luxuries, including tobacco, liquor and leisure activities. Women devoted much more of their income to maintaining better nutritional levels and were more likely to set aside extra money for health care and education.

A more positive aspect of migration is that workers often send home a portion of their wage packets. Remittances from workers in China's booming coastal provinces, for instance, are revitalizing inland rural communities. Migrants from China's most populous interior province, Sichuan, have managed to send back over 30 billion yuan ($3.6 billion) a year to their home villages. This influx of money has opened up new opportunities for rural families. Women left to tend farms are able to pay off debts, buy better equipment, fertilizers and improved seeds, even expand their land holdings. It should be noted, however, that women migrants often send back more money than their male counterparts.

Women as food producers are handicapped in three areas. First, in many developing countries women are in practice barred from inheriting or owning property. Even when there are no males left in the immediate family, the land often passes by custom to a male relative. Second, the systematic neglect of women farmers has marginalized their activities and contributed to "the feminization of poverty". Part of this is accounted for a by a "masculinization of work": where new technologies have been introduced, men have taken the jobs created. According to studies carried out by the International Fund for Agricultural Development over the past 20 years the number of rural women living in absolute poverty increased by 50 per cent from 370 million to about 565 million. Over the same period, the percentage of rural men in absolute poverty increased by only 30 per cent. Third, at a time when there are more women-headed households than ever before struggling to survive on smaller and smaller plots of land or in cramped urban slums, they are given few chances to take advantage of new economic opportunities.

Failure to pay attention to the needs of women farmers in sub-Saharan Africa is partly responsible for Africa's failure to increase food production in line with population growth. Although African women produce 80 to 90 per cent of all food consumed by their families and comprise 60 per cent of the agricultural labour force, they receive less than 1 per cent of the total credit available to agriculture.