According to the UN's Food and Agriculture Organisation, world food prices peaked in the middle of 2008, in what was called then the global food crisis.

But, in the 12 months since then, they've fallen dramatically, as farmers have ramped up production.

The price of some commodities, though, hasn't fallen as much as that of others.

Dairy products and cooking oils have pretty well halved in price since the peak a year ago, but the price of rice, in particular, has fallen far less.

Alexander Sarris, the FAO's trade and markets director, explained why to the BBC's Steve Evans.

First broadcast 13 July 2009