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Early 20th century

During the early 20th century, tin replaced silver as the country's most important source of wealth. A succession of governments controlled by the economic and social elite followed laissez-faire capitalist policies through the first 30 years of the 20th century.

Living conditions of the native people, who constitute most of the population, remained deplorable. With work opportunities limited to primitive conditions in the mines and in large estates having nearly feudal status, they had no access to education, economic opportunity, and political participation. Bolivia's defeat by Paraguay in the Chaco War (1932–1935), where Bolivia lost a great part of the Gran Chaco region in dispute, marked a turning-point.

On 7 April 1943, Bolivia entered World War II, joining part of the Allies, which caused president Enrique Peñaranda to declare war on the Axis powers of Germany, Italy and Japan.

In 1945, Bolivia became a founding member of the United Nations.

The Revolutionary Nationalist Movement (MNR), the most historic political party, emerged as a broad-based party. Denied its victory in the 1951 presidential elections, the MNR led a successful revolution in 1952. Under President Víctor Paz Estenssoro, the MNR, having strong popular pressure, introduced universal suffrage into his political platform and carried out a sweeping land-reform promoting rural education and nationalization of the country's largest tin mines.