Divergence, Big Time
论证了无需历史数据即可证明现代经济史的基本事实是各国人均收入的巨大绝对分化，并给出了1870至1990年间贫富国家收入差距扩大的具体数据。
Historical data are unnecessary to demonstrate that perhaps the basic fact of modern economic history is massive absolute divergence in per capita income across countries. A plausible lower bound on per capita income can be combined with estimates of its current level in the poorer countries to place an upper bound on long-run income growth. Between 1870 and 1990, the ratio of richest to poorest countries' income increased from roughly 9 to 1 to 45 to 1, the standard deviation of (natural log) per capita income doubled, and the average income gap between the richest and all other countries grew nearly tenfold from $1,286 to $12,000.