经验表明，在某一点上 — — 通常是人均收入达到15,000—20,000美元（约为美国水平的三分之一）时 — — 增长开始趋缓。
Experience shows that there is a point – usually when per capita income levels reach about $15,000-20,000 (roughly one-third the level in the United States) – when growth tends to slow.