As many a former factory worker can attest, U.S. companies have invested so heavily in technology that some plants now practically run themselves. This illustrate a rethinking under way on how to measure economic output, a discussion that is leading to an overhaul of government data this week that will show the U.S. economy is a bit larger than previously thought. This will change on Wednesday when the Commerce Department releases decades of revised data that will include R&D as a category of investment. Under the new framework, R&D added about $300 billion to GDP in 2010. This could give...