Innovation was rampant in the computer industry during the late 1960s and the 1970s. Did innovation vastly extend the capabilities of computers or simply reduce the costs of doing the same thing? This question goes to the heart of whether the rate of decline in 'constant-quality' computing...

This paper estimates the importance of network effects in the market for Yellow Pages. I estimate three simultaneous equations: consumer demand for usage of a directory, advertiser demand for advertising and a publisher's first-order condition (derived from profit-maximizing behavior)....