The electric utility industry has been a frequent target of economists studying cost curves. Output is fairly easily defined (electricity produced), and the United States has a large number of independently owned utilities of many different size. Because these companies must regularly deal with state regulatory commissions in rate cases, they collect large volumes of data pertaining to costs and revenues. Utilities have also been observed to have constant productivity improvements and technological progress. The study summarized here was performed using 1971 data for 74 utilities.45 Because the data are for 1971, this study rules out any effects of pollution control equipment on costs.