Three major data sets disagree on country rankings

Comparing year-2000 GDP per capita rankings of sub-Saharan economies across the Maddison, World Development Indicators, and Penn World Tables data sets, Jerven found they agreed on the ranking of only one country—DR Congo, the poorest—and disagreed on all 44 others, with discrepancies as large as the Penn World Tables ranking Liberia second-poorest while Maddison ranked it among the ten richest, and a standard deviation of about 7 ranks.