Focusing on the evils of the subsidies means we have lost sight of a number of the unintended effects and that subsidies are often the least of poor-country farmers' worries.

Read more from Pietra Rivoli in The Guardian

"The removal of subsidies to farmers in wealthy countries would shrink supply and boost world prices. But how much of the price increase would reach poor farmers? Not much. For cotton, while American farmers receive about double the world market price for their crop, farmers in the poorest countries of west Africa generally receive half that price. The rest is eaten up elsewhere in the value chain, often by exploitive practices that work against poor and illiterate farmers who lack political power.

"Economists predict that removing such subsidies could increase world prices for cotton by about 10%, which means west African farmers might see a 5% boost in their incomes. A step in the right direction? Of course. A panacea for rural poverty in west Africa? Not by a long stretch.

"Poor countries, in aggregate, remain net importers of most food crops. Reducing agricultural subsidies might marginally boost poor-country farmers' incomes, but we must recognise that when western taxpayers subsidise farm production, they not only enrich French and American farmers, they also subsidise food consumers all over the world.

"Because developing countries are net importers of food, these countries can look forward to at least some higher food prices as western largesse to farmers is trimmed. This is good news for those who grow food in poor countries, but bad news for those who eat it.

"Cotton is a related case. The huge subsidies paid to US cotton farmers depress the world price of cotton and thereby stimulate US cotton exports, with the result that textile production in poor countries - a vitally important industry for many poor countries - is subsidised by US taxpayers. While reducing subsidies might benefit China's cotton farmers, it will also harm (at least in the short run) its millions of textile workers."