Power inputs from labour, draught animals and machines in the agriculture of the developing countries
建立模型估算90个发展中国家为增产28种作物所需的劳动力、役畜和机器动力投入，发现1980-2000年总动力和劳动力投入年增长率分别为2.2%和2.1%，就业弹性为0.52，机械化在较高收入国家推进最快。
This article describes a model developed and used to estimate power input requirements by source for increasing agricultural production in the developing countries. Production increases are defined for 28 crops, each of which is grown in one or more of six classes of rainfed and irrigated land at specified yield levels. The estimation and analysis is carried out for each one of 90 developing countries, which together account for 98% of the population of the developing world, not counting China. Given crop production increases specified as above, the model calculates first the requirements for total power input and subsequently distributes it to the three sources of power (labour, machinery and draught animals). The results show that for a 3.5% annual increase in crop production in the aggregate of the 90 developing countries 1980–2000 (the growth rate 1966–81 was 2.9%) the total power input (in terms of man day equivalents) should grow at 2.2% and the labour input at 2.1%, implying an employment elasticity of 0.52. Mechanization should advance most rapidly in the higher income developing countries (Latin America, Near East), while in all regions, animal traction would be substituted by machinery.