Homogeneity masquerading as variety: the case of horizontal innovation models
指出水平创新文献中的代表性模型共享两个关键假设，导致中间产品实际上是同质的，所谓多样性增长只是单一同质中间产品数量的增加。
The literature on ‘horizontal innovation’ claims to analyse cases where unbounded endogenous growth comes from an increasing variety of intermediate goods. The present paper contends that a good sample of representative models in this literature share two essential assumptions regarding production technology, and that these assumptions together amount to assuming the homogeneity of various intermediate goods. In these models, there is no variety of intermediate goods to increase owing to R&D activities; what increases is a mass of a single homogeneous intermediate good.