据经合组织估计截止2030年全球中产阶级（定义为按2005年购买力平价计算，每人日均开支达10-100美元的家庭）将膨胀至49亿人，而2009年还仅有18亿的规模。
The OECD estimates that the global middle class (defined as households with daily expenditures of $10-100 per person, in 2005 purchasing power parity terms) will swell to 4.9 billion people by 2030, from 1.8 billion in 2009.