Stocks tumbled this morning after the release of a grim forecast by the World Bank. The Dow tumbled about 100 points, while the Nasdaq and S&P each dropped 1.6%. The World Bank predicted the economy would shrink 2.9% this year, a big downward revision from its previous forecast of a 1.7% drop. Commodities were declining, with oil down more than a dollar to $68 a barrel. (More stock market stories.)