Updated August 13, 2015: This new edition includes corrected estimates for Iceland, Luxembourg, the Netherlands and Taiwan, and some related aggregated data.

This report examines changes in the distribution of the global population by income from 2001 to 2011. Of special interest is the change in the global middle-income population, or the global middle class. The analysis encompasses 111 countries, which accounted for 88% of the global population and 85% of world output in 2011. The study is among the first to make use of 2011 purchasing power parities (PPPs) that are based on the latest available benchmark estimates of price levels around the world.

Estimates are presented for the world and for the major regions, such as Asia & South Pacific, Africa, and Europe. The report also highlights trends in selected major countries, such as in China and India; trends in the U.S. and other advanced economies; and developments in Eastern Europe.

The key data sources for this report are the World Bank PovcalNet database (Center for Global Development version available on the Harvard Dataverse Network) and the Luxembourg Income Study database.

This report is a collaborative effort based on the input and analysis of the individuals listed below. In addition, Fatima Ghani made key contributions in the earlier stages of the research. Find related reports online at pewresearch.org/global

Rakesh Kochhar, Associate Director, Research
Michelle Atkinson, Data Architect
Renee Stepler, Research Assistant
Anna Brown, Research Assistant
James Bell, Vice President, Global Strategy
Claudia Deane, Vice President, Research
Diana Yoo, Art Director
Bill Webster, Information Graphics Designer
Ben Wormald, Associate Digital Producer
Danielle Alberti, Web Developer
Dana Amihere, Web Developer

This report divides the population in each country into five groups based on the daily per capita consumption or income of a family. The use of both measures is necessitation because for some countries, such as India and China, only consumption data are available, and for other countries, such as Brazil and Argentina, only income data are available. The terms “income” and “consumption” are used interchangeably, and people are referenced with respect to their “income” status.

The five income groups are people who are poor and living on $2 or less daily, low income ($2.01-10), middle income ($10.01-20), upper-middle income ($20.01-50), and high income (more than $50). For ease of exposition, the report refers to income ranges in whole numbers, such as $10-20 in reference to who is middle income.

All dollar figures are expressed in 2011 prices and converted to 2011 purchasing power parity dollars. Purchasing power parities (PPPs) are exchange rates adjusted for differences in the prices of goods and services across countries.

The terms “middle income” and “middle class” are used interchangeably in the report, as are the terms “poor” and “in poverty.”

The estimates of population distributions by income are for 2001 and 2011. For most countries, however, survey data from exactly those two years are not available. Thus, the distributions for 2001 and 2011 are typically estimated by projecting changes in income or consumption from the dates of the surveys to either 2001 or 2011.

Percentage point changes, sums, differences and other computations are done before numbers are rounded.