United States. Central Intelligence Agency, The 2003 CIA World Factbook
“ In contrast, the currency exchange rate method involves a variety of international and domestic financial forces that often have little relation to domestic output. In developing countries with weak currencies the exchange rate estimate of GDP in dollars is typically one-fourth to one-half the PPP estimate. Furthermore, exchange rates may suddenly go up or down by 10% or more because of market forces or official fiat whereas real output has remained unchanged. ”
