The Dow Jones Transportation Average dropped 0.8% in afternoon trade Thursday, which looks particularly weak when compared with the 130-point, or 0.8% gain in the Dow Jones Industrial Average . Weighing on the transports barometer, JetBlue Airways Corp.'s stock slid 6.4% and tank barge operator Kirby Corp. shares shed 4.2%. What's concerning about the Dow transports' selloff, is that according to the century-old Dow Theory of market analysis, the Dow transports "must 'confirm' the movement of the industrial average for a market trend to have staying power," according to S&P Dow Jones Indices. The idea is, the transports take what the industrials make, so "if the transports aren't taking what the industrials are making, it portends economic weakness and market problems," according to S&P Dow Jones Indices. The Dow transports are now down 17% over the past three months, while the Dow industrials are down 9.6%.
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