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Hanlon, W. W. (2015). Necessity is the mother of invention: Input supplies and Directed Technical Change. Econometrica, 83(1), pp. 67-100.

چکیده مقاله

This study provides causal evidence that a shock to the relative supply of inputs to production can (1) affect the direction of technological progress and (2) lead to a rebound in the relative price of the input that became relatively more abundant (the strong induced-bias hypothesis). I exploit the impact of the U.S. Civil War on the  ritish cotton textile industry, which reduced supplies of cotton from the Southern United States, forcing British producers to shift to lower-quality Indian cotton. Using detailed new data, I show that this shift induced the development of new technologies that augmented Indian cotton. As these new technologies became available, I show that the relative price of Indian/U.S. cotton rebounded to its pre-war level, despite the increased relative supply of Indian cotton. This is the first paper to establish both of these patterns empirically, lending support to the two key predictions of leading directed technical change theories.

قسمتی از بخش انتهایی (نتیجه گیری) مقاله

The study provides evidence that the temporary reduction in the supply of American cotton during the U.S. Civil War caused directed technical change focused on the main alternative input, Indian cotton. While similar, American and Indian cotton differed in important ways, and innovators focused their efforts on technology types that addressed these differences. Moreover, as these new technologies were introduced, the relative price of Indian to U.S. cotton rebounded to (and in some years above) the average level observed during the pre-war period, despite a substantial increase in the relative supply of Indian to U.S. cotton. Directed technical change theories, such as Acemoglu (2002), can potentially explain the innovation and relative price movements of Indian cotton if the elasticity of substitution between U.S. and Indian cotton is sufficiently high (near 2), as is suggested by Irwin (2003). Alternative theories may also have the potential to explain the patterns I identify. For example, perhaps innovators simply focused on reducing waste and this was more easily accomplished for Indian cotton than for other varieties. However, we do not observe increased innovation in other major waste-producing technologies, such as combing machines, so this explanation seems unlikely. A more compelling alternative is that innovation may have been a result of learning-by-doing and the switch to production of machines more suited to Indian cotton. Differentiating between directed technical change and learning-by-doing is an interesting direction for future research.