Felix Salmon thinks says that the "financial sophisticates know that the Dow Jones Industrial Average is a bit of a joke: it's only 30 stocks, and it's not even an index."

Typically the Dow and the S&P move pretty much in line with each other. But yesterday (March 17th), with Dow component JP Morgan rising by $3.40 per share, the Dow is actually up, even as the markets generally are significantly down. The last time there was a gap of over 100bp between the daily movements on the Dow and the S&P 500 was July 18, 2002, when the S&P 500 fell 2.7%, but the Dow fell only 1.56% and again on September 13, 2002.