Increases in population have usually been accompanied (indeed facilitated) by an increase in trade. In the Western experience, commerce provided the conditions that allowed industrialization to get started, which in turn led to growth in science, technology, industry, transport, communications, social change, and the like that we group under the broad term of “development.” However, the massive increase in population that in Europe was at first attributed to industrialization starting in the eighteenth century occurred also and at the same period in China, even though there was no comparable industrialization.

It is estimated that the Chinese population by 1600 was close to 150 million. The transition between the Ming and Qing dynasties (the seventeenth century) may have seen a decline, but from 1741 to 1851 the annual figures rose steadily and spectacularly, perhaps beginning with 143 million and ending with 432 million. If we accept these totals, we are confronted with a situation in which the Chinese population doubled in the 50 years from 1790 to 1840. If, with greater caution, we assume lower totals in the early eighteenth century and only 400 million in 1850, we still face a startling fact: something like a doubling of the vast Chinese population in the century before Western contact, foreign trade, and industrialization could have had much effect.

To explain this sudden increase we cannot point to factors constant in Chinese society but must find conditions or a combination of factors that were newly effective in this period. Among these is the almost complete internal peace maintained under Manchu rule during the eighteenth century. There was also an increase in foreign trade through Guangzhou (southern China) and some improvement of transportation within the empire. Control of disease, like the checking of smallpox by variolation may have been important. But of most critical importance was the food supply.

Confronted with a multitude of unreliable figures, economists have compared the population records with the aggregate data for cultivated land area and grain production in the six centuries since 1368. Assuming that China’s population in 1400 was about 80 million, the economist Dwight Perkins concludes that its growth to 700 million or more in the 1960s was made possible by a steady increase in the grain supply, which evidently grew five or six times between 1400 and 1800 and rose another 50 percent between 1800 and 1965. This increase of food supply was due perhaps half to the increase of cultivated area, particularly by migration and settlement in the central and western provinces, and half to greater productivity—the farmers’ success in raising more crops per unit of land.

This technological advance took many forms: one was the continual introduction from the south of earlier-ripening varieties of rice, which made possible double-cropping (the production of two harvests per year from one field). New crops such as corn (maize) and sweet potatoes as well as peanuts and tobacco were introduced from the Americas. Corn, for instance, can be grown on the dry soil and marginal hill land of North China, where it is used for food, fuel, and fodder and provides something like one-seventh of the food energy available in the area. The sweet potato, growing in sandy soil and providing more food energy per unit of land than other crops, became the main food of the poor in much of the South China rice area.

Productivity in agriculture was also improved by capital investments, first of all in irrigation. From 1400 to 1900 the total of irrigated land seems to have increased almost three times. There was also a gain in farm tools, draft animals, and fertilizer, to say nothing of the population growth itself, which increased half again as fast as cultivated land area and so increased the ratio of human hands available per unit of land. Thus the rising population was fed by a more intensive agriculture, applying more labor and fertilizer to the land.

人口增长通常伴随着（事实上促进了）贸易的增加。按照西方的经验，商业为工业化的开始提供了条件，而工业化反过来又导致了科学、技术、工业、交通运输、通信进步和社会变化等等，我们把这些统称为“发展”。但是，十八世纪开始的工业化带来了欧洲的人口大幅增长；同时间中国的人口也暴涨，尽管中国没有经历类似的工业化。 据估计，到1600年中国的人口已经接近1亿5000万。明清之交（十七世纪）人口数量可能有所减少，但从1741年到1851年，人口数量每年都稳步上升，从1亿4300万涨到了4亿3200万，相当惊人。如果我们认为这些合计数字没问题，我们将面临这样一个情形：从1790年到1840年，中国人口在这50年间翻了一番。如果谨慎一些，我们假设在18世纪初总人数要少一些，到1850年也只有4亿的话，事实依然让人吃惊：在与西方接触、对外贸易和工业化之前，中国庞大的人口数量翻倍本应产生很大的影响。 要解释这种突然的人口增加，我们不能指向中国社会的一些一直不变的因素，而是必须找到当时新出现的一系列条件或诸多组成因素。其中包括十八世纪的中国处于满族统治下，国内几乎完全和平。广州（华南）的对外贸易也有所增加，国家内部的交通也有所改善。还有一个重要因素是疾病的控制，如通过人痘接种来克制天花。但这当中最重要的还是食品供应。 面对大量的不可靠的数据，经济学家将1368年以来的6个世纪的人口统计记录与耕地面积和粮食生产总量的综合数据进行了比较。经济学家德怀特•帕金斯得出结论，假设在1400年中国的人口是8000万左右，由于粮食产量稳步增长，到20世纪60年代人口是有可能增长到7亿人的，明显地从1400年到1800年增长了5到6倍，从1800年到1965年又增长了50%。粮食供应的增加可能一半是由于耕地面积的增加，特别移民并定居到中西部省份带来的耕地面积增加；另一半是由于生产力的提高——农民成功提高了每单位土地面积的粮食产量。 技术进步有许多形式：一个是不断从南方引进早熟的水稻品种，这种水稻可以一年两熟（一块地每年收获两季）。新作物如玉米、红薯、花生和烟草从美洲传进来。拿玉米来说，可以在干燥的土壤和华北边缘的山地种植，可用作食品、燃料、饲料，提供了当地七分之一的食物能量。红薯可以在沙质土壤中种植，由于每单位土地面积提供的食物能量比其他作物都多，所以成为了华南水稻种植地区穷人们的主要食品。 资本的投入也提高了农业生产力。首先是灌溉方面，从1400年到1900年，总灌溉土地似乎增加了近三倍。农用工具、役畜和肥料方面都有进步，更不用说人口本身也有增长，增速是耕地面积增速的一半，因此增加了人均可用土地面积的比例。这种更加密集的农业生产为增长的人口提供食物，而人口为土地提供更多的劳动力和肥料。