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Poverty measurement and PPPs: The World Bank explains

LTD Editors's picture

As the editors of Let's Talk Development, we want to respond to questions raised recently in social media channels about use of 2011 International Comparison Program (ICP) as well as during events and discussions about poverty and measurements during the Annual Meetings of the World Bank and IMF last week.

The World Bank currently uses an international poverty line of $1.25 (per person per day) in 2005 prices to monitor global poverty. The process draws on several data sources, including the ICP. The most recent  global and regional poverty estimates cover the period 1981-2011 and are available from the recently updated Povcalnet database; they are based on data from well over 1,000 household surveys, covering nearly all developing countries. The latest estimates have been published and  explained in both the recent Policy Research Report and the Global Monitoring Report, published last week.

The end of a long era

Branko Milanovic's picture

Is China, after a hiatus of 150 years, again the largest economy in the world? Not all sources of GDP data agree, but there is little doubt that China is either already now the largest economy, or it will, within a year, become so by overtaking that of the United States. Whichever the case may be, a long era when the American economy was the largest in the world and which began around 1860, is now reaching its end.

Data on gross domestic product (called now Gross Domestic Income) are available from three sources: the Maddison project, which is the only source for the long-run series of national GDPs, going back to 1820s; the World Bank or IMF annual data, going back to 1960; and Penn World Tables, produced periodically at the University of Pennsylvania, going back from their just-released version 8.0 to 1950 . All three sources produce GDP data in PPP (purchasing power parity) terms, which means that they adjust for differences in price levels between the countries. The easiest way to explain it is to say that PPPs try to account for each good and service using the same price for it around the world, so that a mobile phone, a kilo of rice and a haircut would each be valued the same in China as in the United States. Only thus can the real sizes of the economies, and the welfare of people, be truly comparable. These PPP data, in turn, are obtained through a massive worldwide project called the International Comparison Program, which is run every five to 10 years and collects more than 1,000 prices in all countries.