Implications of agricultural elasticities

Michael Roberts summarizes one of his latest projects in three minutes (speaking time). For those not enamored of econometrics (e.g. why he uses weather as an instrument), his conclusion is:

Globally the demand elasticity for these crops combined is about 0.05 and the supply elasticity is about 0.10, perhaps a little larger. Both of these elasticities are far greater than they would be if estimated using traditional econometric methods that do not account for the joint-dependency of prices on supply and demand. If applied to US ethanol policy, they suggest US ethanol subsidies have caused about a 30% increase in prices for these key commodities and about a 35 million acre expansion of cropland worldwide. That's about the size of North Carolina, the state where I live.

A 30% price increase from biofuels alone is quite substantial. If I recall correctly, IFPRI estimated that biofuels accounted for 30% of the total recent rise in food prices (note the distinction from the absolute 30% implied by Michael's work). Other estimates varied widely, going up to 75% of the total rise in an unreleased but leaked World Bank report that caused quite a bit of controversy.

This also reminds me how inelastic demand makes farmers oppose climate change legislation.