This analysis defined the global middle class as people earning $4,286 or more per year in PPP units – standardized international dollars. This threshold was based on a definition of the global middle class put forth by the International Bank for Reconstruction and Development/The World Bank in 2007.6

The 2007 report defined the “global middle class” as people earning between $4,000-$17,000 per capita in 2005 PPP dollars. This range of $4,000-$17,000 was adjusted to account for the fact that it related to income for 2005 yet was used to categorize income for 2007. The adjustment involved accounting for GDP growth per capita.

Pew Global Attitudes income data are self-reported, categorical, household-level data in the national currency of the country in which the respondents were surveyed. The income data were adjusted to account for household size and converted into standardized international dollars (PPP units).

Respondents were then organized into two groups: those whose incomes met or exceeded the middle class income threshold – $4,286 (PPP) – and those whose incomes did not (lower income).