The bears have had a very tough couple of months while global markets have responded to better economic news and anticipation of the latest round of quantitative easing. The summer talk about a double-dip recession has slowly faded away, and most of the talking heads I see on television have become uber-bullish. This may be a sign that the market is overheated, but if the bears wanted a more objective measure, they can point to the recent decline in the Baltic Dry Index.

The global shipping index has now declined for nine straight days as of Tuesday, which has hit shipping prices by more than 10% during the slide. The Baltic Dry Index (BDI) is a survey of shippers like DryShips (Nasdaq: DRYS) and Excel Maritime (NYSE: EXM) that are involved in transporting commodities like metals, grains, cement, fertilizers, and fossil fuels by sea to determine the market price for shipping these goods.

Many look to the BDI as a key indicator of the economy, because the goods that are shipped are important components for manufacturing and production. As the global economy came to a halt in 2008 when the financial crisis spread, the BDI dropped 94% from May to December.

The current decline in the index may end up being just a small blip in the global recovery, but at least it should provide some fodder for wounded bears. Investors may want to keep an eye on the index as well as the action in dry bulk shipping stocks like Genco Shipping (NYSE: GNK) and Diana Shipping (NYSE: DSX) to see if this slide has legs.

Do you think this Baltic Dry Index decline could be pointing to a pullback in the equity markets? Let us know in the comments box below.

Andrew Bond doesn't own shares in the companies listed. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Fool has a disclosure policy.