Comparison of GDP Per Capita Data in Penn World Table and World Development Indicators

This paper compares data on GDP per capita, which is used in almost every cross-country study, from two different sources which are used by numerous researchers and other users throughout the world. The methodology consists of taking GDP per capita in international dollars for the ICP benchmark year 2005 for each country from World Development Indicators 2012 CD-ROM (WDI) and Penn World Table 7.1 (PWT), which are the current (2012) versions of these well-known sources. A similar exercise is undertaken for World Development Indicators 2011 CD-ROM and Penn World Table 7.0, which are the last versions of the data. The WDI and PWT data are also compared with the benchmark estimates from the last International Comparison Program (ICP). Huge differences are found between the two sources for numerous countries in both the current and the last versions. The number of countries for which WDI and the ICP benchmark numbers show huge differences is small, but there are many countries for which PWT and the ICP benchmark numbers show large differences. The study seems important for judging how data on this crucial variable from two most widely used sources agree or differ. The reported huge differences suggest that the users may exercise caution in drawing strong conclusions from information derived from either source, and may consider doing some sensitivity checks based on data from the other source. A simple illustration is provided to indicate how use of data from each source might affect the results.