NOTE: Country rankings of the type presented below cannot pretend to be definitive; instead they aspire only to provide the reader with an approximation of the high and low ends on a particular scale. Country data vary enormously depending on the sources, and the absence of reliable data on some countries requires their omission, which further skews the results. Only countries for which statistics were available in sources 1 and 2 figure in these lists. Sources: 1. The World Factbook, 2011. 2. U.S. Census Bureau, International Database.