?In response to the price-raising actions of OPEC, nationalization of overseas concessions, and the diminution of reserves in the US, the US petroleum industry should have changed considerably in structure and scope of activities since the 1950s. The author explores whether these changes have occurred by examining the reports of all public US oil companies as summarized in standard commercial reference books. Ghosh notes that changes in the distribution of sizes of firms and in the market shares of the largest firms are the most important structural elements in an industry. Other crucial factors are the degree of vertical integration from raw material production to finished products distribution, ease of entry into the industry, and product differentiation both inside and outside the industry. Observing these elements and summarizing them in a series of statistical tables, the author concludes that significant changes in the industry have taken place since the 1950s. Outstanding are changes in the ranking of the size of firms and product differentiation by entry into other economic activities... Ghosh offers much material, but readers must arrive at their own conclusions. This work is also a good educational device in how to find material on the behavior of firms.?-CHOICE