David Hightower on the Explosion in Commodities Markets

David Hightower, principal of commodity trading adviser Hartfield Management and editor of newsletter, has dealt in commodities for more than 25 years. At the start of his career, prices in the agricultural commodities markets were dictated largely by what happened in a "500-mile circle around Decatur, Ill.," he says. "Now influences come from every corner of the world, and that's increased volatility." Contributing Editor Christopher Farrell reached Hightower in Chicago.

Is the agricultural commodity boom becoming a bubble?