http://www.slate.com/id/2090303/
Obscure Economic Indicators: the Baltic Dry Index measures the cost of shipping raw materials, which makes it a good indicator of “economic growth and production.”
“After all, it doesn’t deal with container ships carrying finished goods. It deals with the precursors to production: bulk carriers carrying building materials, cement, grain, coal, and iron. Unlike stock and bond markets, the BDI ‘is totally devoid of speculative content,’ says Howard Simons, an economist and columnist at TheStreet.com. People don’t book freighters unless they have cargo to move.”