Frankel theory on high commodity prices

Jeffrey Frankel is Brad Setser's guest blogger for a few days. He's focussing on why commodity prices are up if the global economy has turned down. His answer? Real interest rates:

If strong economic growth is not the explanation for the large increases since 2001 in prices of virtually all mineral and agricultural commodities, then what is? One wouldn’t want to try to reduce commodity markets to a single factor, nor to claim proof of any theory by a single data point. Nevertheless, the developments of the last six months provided added support for a theory I have long favored: real interest rates are an important determinant of real commodity prices.

High interest rates reduce the demand for storable commodities, or increase the supply, through a variety of channels:
- by increasing the incentive for extraction today rather than tomorrow (think of the rates at which oil is pumped, gold mined, forests logged, or livestock herds culled)
- by decreasing firms’ desire to carry inventories (think of oil inventories held in tanks)
- by encouraging speculators to shift out of spot commodity contracts, and into treasury bills.

All three mechanisms work to reduce the market price of commodities, as happened when real interest rates where high in the early 1980s. A decrease in real interest rates has the opposite effect, lowering the cost of carrying inventories, and raising commodity prices, as happened in the 1970s, and again during 2001-2004. It’s the original “carry trade.”

Professor Frankel is cross-posting this material on his own blog too.