Why have rice prices surged to record highs?

Asian rice prices have almost trebled this year and prices on the Chicago Board of Trade have risen more than 80 percent to hit successive record highs as export restrictions by leading suppliers fuel insecurity over food supplies.

With only 30 million tonnes traded annually, government supply curbs, such as those from New Delhi and Hanoi, have spooked importers, such as the Philippines and Bangladesh, at a time when global stocks have halved since hitting a record high in 2001.

Export curbs:

October 2007 - India, which was the world's second-largest rice exporter last year but is set to lag behind Thailand and the United States this year, bans exports of non-basmati rice to rein in prices and control inflation, but later in the month eased the ban on some superior varieties of the grain.

March 2008 - India bans exports of non-basmati rice again as inflation hits a 14-month high, alarming policymakers. March 2008 - Egypt bans rice exports from April 1 to October to hold down local prices. The country normally produces about 4.6 million tonnes a year of white rice, leaving a domestic surplus of about 1.4 million tonnes for export.

April 2008 - Vietnam, due to regain its position as the No. 3 exporter this year, extends a ban on rice sales until June to help stabilise domestic food prices as it tries to tame double-digit inflation. Prior to that, it had curtailed exports for March and April.

April 2008 - Brazil temporarily suspends rice exports to safeguard domestic supply and keep prices of the basic foodstuff stable. Brazil, which is not a major global rice supplier, exported 313,000 tonnes of rice last year. April 2008 - Indonesia, Southeast Asia's largest rice consumer, says it would curb medium-grade rice exports to combat inflation.

Under Indonesia's new rice export rules, state procurement agency Bulog is allowed to sell medium-grade rice overseas only when national stocks are above 3 million tonnes and domestic prices are below a government's target price. April 2008 - India slaps export taxes on basmati rice, on top of an existing ban on non-basmati rice exports.