These are lists of regions and countries sorted by their estimated real gross domestic product (GDP) in terms of purchasing power parity (PPP), the value of all final goods and services produced within a country/region in a given year. GDP dollar (international dollar) estimates here are derived from PPP estimates.
In some of these lists, the term country corresponds to the geographical region of the country being referred to, not the country itself. Most of the information below is based on estimates by economic historian Angus Maddison, former professor at University of Groningen and assistant director of the economics development division for the Organisation for Economic Co-operation and Development, in his work The World Economy: Historical Statistics. Estimates are for the periods from the 1st century to 1998, with figures in millions of international dollars, and shares of world GDP are also given.
Maddison' assumptions have been criticized and admired by academics and journalists. Bryan Haig, who has characterized Maddison's figures for 19th century Australia as "inaccurate and irrelevant"[1], by John Caldwell, in whose assessment Maddison's arguments have a "dangerous circularity"[2], by W. W. Rostow, according to whom, "This excessive macroeconomic bias also causes him (Maddison) to mis-date, in my view, the beginning of what he calls the capitalist era at 1820 rather than, say, the mid-1780s[3], and by W. J. MacPherson who has described Maddison's work on India and Pakistan of using "dubious comparative data."[4]
Economist and Journalist Evan Davis has praised Maddison's research by citing it as a "fantastic publication" and that it was "based on the detailed scholarship of the world expert on historical economic data Angus Maddison." He also added that "One shouldn't read the book in the belief the statistics are accurate to 12 decimal places."[5]
NicholasD.Kristof：Glory      is as ephemeral as smoke and clouds