CONSUMERS can be forgiven if they haven't noticed that today's clothes dryers offer more bang for the buck than they did a few years ago. They'll still dry your towels, but the government thinks you are enjoying the machines more. Same for refrigerators, as well as college textbooks, microwave ovens and audio equipment. In fact, over the next few years the government promises to keep track of hundreds of other everyday items to determine how technological changes — or, more often, just the elimination of older models — affects the price. But this isn't just some arcane project aimed at...