The U.S. Demographic Transition
研究1800至1940年美国人口从高生育率、高农村比例向低生育率、高城市比例的转型，认为农业和制造业的技术进步是主因。
Between 1800 and 1940 the U.S. went through a dramatic demographic transition. In 1800 the average woman had 7 children, and 94 percent of the population lived in rural areas. By 1940 the average woman birthed just 2 kids, and only 43 percent of populace lived in the country. The question is: What accounted for this shift in the demographic landscape? The answer given here is that technological progress in agriculture and manufacturing explains these facts.