Real exchange rate calculated as PPP/xrat, since xrat is foreign price of domestic (US) currency.
Heston, A., R. Summers, and B. Aten. 2006. Penn World Table Version 6.2. Center for International Comparisons of Production, Income, and Prices, University of Pennsylvania. http://www.rug.nl/ggdc/productivity/pwt/pwt-releases/pwt-6.2.
Source: Data from Penn World Table 6.2.