Most energy crises have been caused by localized shortages, wars and market manipulation. Some have argued that government actions like tax hikes, nationalisation of energy companies, and regulation of the energy sector, shift supply and demand of energy away from its economic equilibrium.However, the recent historical energy crisis listed below were not caused by such factors. Market failure is possible when monopoly manipulation of markets occurs. A crisis can develop due to industrial actions like union organized strikes and government embargoes. The cause may be over-consumption, aging infrastructure, choke point disruption or bottlenecks at oil refineries and port facilities that restrict fuel supply. An emergency may emerge during very cold winters due to increased consumption of energy.