, Qatar has the fourth highest GDP per capita in the world, according to the International Monetary Fund. It relies heavily on foreign labor to grow its economy, to the extent that migrant workers compose 86% of the population and 94% of the workforce. Qatar has been criticized by the International Trade Union Confederation. The economic growth of Qatar has been almost exclusively based on its petroleum and natural gas industries, which began in 1940. Qatar is the leading exporter of liquefied natural gas. In 2012, it was estimated that Qatar would invest over $120 billion in the energy sector in the next 10 years. The country was a member state of Organization of Petroleum Exporting Countries (OPEC), having joined in 1961, and having left in January 2019.