Economics are a bit perplexed by the productivity slowdown, especially since it seems to be afflicting all industrialized economies at the same time. Indeed, the U.S. is doing better than most. Northwestern's Gordon maintains that it's the result of a secular end to a long technological cycle — that the low-hanging fruit of innovation-driven gains has been picked: the first industrial revolution, air conditioning, automobiles, computers and communications and the replacement of small stores by big-box chains.