One controversial introduction of energy market concepts and privatization to electric power systems took place in Chile in the early 1980s, in parallel with other market-oriented reforms associated with the Chicago Boys. The Chilean model was generally perceived as successful in bringing rationality and transparency to power pricing. Argentina improved on the Chilean model by imposing strict limits on market concentration and by improving the structure of payments to units held in reserve to assure system reliability. One of the principal purposes of the introduction of market concepts in Argentina was to privatize existing generation assets (which had fallen into disrepair under the government-owned monopoly, resulting in frequent service interruptions) and to attract capital needed for rehabilitation of those assets and for system expansion. The World Bank was active in introducing a variety of hybrid markets in other Latin American nations, including Peru, Brazil, and Colombia, during the 1990s, with limited success.