20th century

== Economics ==
* The [[Great Depression]] was a worldwide [[economic slowdown]] that lasted throughout the early 1930s.
* The [[Soviet Union]] implemented a series of [[Five-year plans for the national economy of the Soviet Union|five-year plans]] for industrialization and economic development.
* Most countries abandoned the [[gold standard]] for their currency. The [[Bretton Woods system]] involved currencies being [[Fixed exchange-rate system|pegged]] to the United States dollar; after the system [[Nixon shock|collapsed in 1971]] most major currencies had a [[floating exchange rate]].
* Economics was divided into two general economic schools: Keynesian and neoclassical
* The [[1970s energy crisis]] occurred when the [[Western world]], particularly the United States, Canada, Western Europe, Australia, and New Zealand, faced substantial petroleum shortages as well as elevated prices. The two worst crises of this period were the [[1973 oil crisis]] and the [[1979 oil crisis|1979 energy crisis]], when, respectively, the [[Yom Kippur War]] and the [[Iranian Revolution]] triggered interruptions in [[Middle East]]ern oil exports.