Tao Ran: I feel that ordinary people, especially China people, pay more attention to the second half of the above logic in their understanding of Malthusian theory, that is, population growth will bring about the phenomena of diminishing marginal income and declining per capita income, and thus the population threat theory becomes popular. However, Malthus' conclusion, whether it is an analysis of economic and social development since the industrial revolution or whether it is applicable to the situation before the industrial revolution, is doubtful.
Dong Xian 'an: According to some scholars, Malthus's analysis at that time was mainly a regular summary of his previous historical phenomena, because the relative proportion of non-agricultural industries at that time was relatively small and could not provide more employment opportunities. Most people look for food on limited and basically fixed land, so the increase of population will inevitably lead to the decrease of marginal income and per capita income. For example, Dan Usher, an American economist, published an article in American Economic Review, suggesting that the fundamental mechanism of China dynasty change lies in the pressure brought by periodic overpopulation, reduced surplus and unsustainable financial situation. These pressures must be released through war and population decline. This view is also very popular among many China historians, and forms the basis for many people to demonstrate that overpopulation in China will bring problems. Fei Zhengqing and other famous American China historians hold similar views. He thinks that the population of China doubled in the18th century, which was accompanied by the growth of commercial economy. By the19th century, the balance between land and population was broken due to the rapid increase of population.
Tao Ran: Actually, the extent to which Malthus' viewpoint is applicable to the historical era before the industrial revolution is worth further discussion. For example, Bosup, a famous economist who studies the relationship between economic development and technological change, found that even in the absence of industrial revolution, population growth has promoted people to carry out more intensive labor and technological innovations that can obtain higher land yield per unit area, such as increasing multiple cropping, using animal power, chemical fertilizers and adopting some new farming techniques, thus leading to the so-called "demand-driven" technological progress. In other words, even before the industrial revolution, the increase in population did not necessarily reduce the per capita output and surplus.
Dong Xian 'an: As you said, whether the population pressure in Malthus accords with historical facts deserves our further study. As Lin Yifu said, before the Ming and Qing Dynasties, China maintained a leading position in technology in the world, largely because of the relatively large population of China. The larger the population, the more people with inventive talents, and the more technological innovations. This conclusion applies at least to the development of science and technology before the industrial revolution, which mainly comes from the dispersion and isolated innovation of talents.