These kinds of projections have often been based on simple extrapolations of exponential trends. Over two or three decades, substantial differences in compound growth rates quickly generate huge changes in economic size or per capita income.
这类预测通常基于简单的指数趋势外推。在20或30年的时界上，复合增长率的重大差异能很快造成经济规模和人均收入上的巨大变化。