In 1937, after the disastrous Chaco War, which was ostensibly fought over oil reserves near the border with Paraguay, Bolivia expropriated the holdings of the Standard Oil Company and formed its own state oil firm, ypfb. However, national control over natural resources declined after 1955, when the Revolutionary Nationalist Movement (mnr) government, as a concession to the United States, passed a new petroleum code favoring U.S. companies. The Bolivian Gulf Oil Company soon became the largest hydrocarbon producer in the country. In the 1960s, under the right-wing dictatorship of René Barrientos Ortuño, new concessions were granted to...