

In comments on the previous post, Ian Castles AO, the former Australian Statistician, notes that the World Bank and IMF create confusion in their reports by mixed use of market-exchange-rate (MER) and purchasing-power-parity (PPP) bases for estimating output and growth. Simply, using market exchange rates to compare the value of output among countries over-estimates the size of developed economies and under-estimates the size of developing economies. This confusion affects their analyses of, among other things, trade data.
The charts (click the thumbnails), taken from the two sets of data prepared by the IMF, show the dramatic difference between MER and PPP bases for comparing output and growth. Using the PPP basis for comparison, developing countries’ economies are much larger in relation to developed economies and projected to ‘close the gap’ sometime after 2015 (take the IMF projections with a grain of salt: they’re just ‘straight line’ extensions of current patterns of growth). The only difference between the two charts is the identification of China. Note that using a PPP basis for comparison, China appears less dominant in the developing country group.