Chart of the week: wheat mountain weighs on prices

In 2008, wheat prices briefly spiked above $13 a bushel, sparking food riots in emerging markets. Since then, the price of the world's most commonly consumed food grain has slumped by more than 70%, with benchmark US futures now at a ten-year low below $4, says Gregory Meyer in the FT.

Harvests have been plentiful in most major producers. In the US, farmers have run out of space in silos and are stockpiling wheat outside, while Russia, likely to become the top exporter this year, also faces storage problems.

Global supply is set to hit a record 743 million tonnes this year.