Bears came out in force Thursday, swatting the indexes solidly south. The Nasdaq chopped off 1.6%, while the S&P 500 pruned 0.8%. The IBD 50 led the carnage with a vicious 2.9% drop. Volume rose on both major exchanges. The action met the definition of a distribution day — a loss in rising volume that points to institutional selling. Few stocks escaped Thursday’s sell-off.