Date
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Maddison, A., (2010) ‘Statistics on world population, GDP and GDP per capita, 1-2008 AD’ Historical Statistics, Groningen Growth and Development Centre.
International Monetary Fund (2012) World Economic Outlook, April 2012, IMF, Washington DC.
United Nations (2011) World population prospects: the 2011 revision, Department of Economic and Social Affairs, Population Division, New York.
World Bank (2012) Worldwide Governance Indictors, World Bank, Washington DC.