It should come as no surprise that the Dow Jones Industrial Average continues its meteoric rise past 36,000 — even with the Federal Reserve’s long-anticipated “tapering” (buying fewer bonds) starting later this month. After all, a balloon goes up when it gets inflated. But how much of this apparent growth is real, and how much is a meaningless illusion?

The Commerce Department’s report on third-quarter GDP sheds light on the subject. Economic growth was disappointing, increasing at a torpid 2.0% annualized rate, far below expectations. But the real devil is in the details.