Diffusion and Multiple Equilibria

拟议的研究议程包括三个主要部分。第一部分主要涉及技术创新扩散的实证研究，以及这种扩散如何影响产出的总体行为。更具体地说，它关注的是根据创新的时间路径和它们扩散的速度来解释GNP的时间序列行为。这被表示为一个随机简化形式的方程，它将当前GNP的创新与过去具有各种滞后的创新联系起来。例如，通过专利申请来衡量的关于国民生产总值增长率和创新活动的横断面国家数据，然后被用来估计方程式的参数。研究的第二部分包括关于企业采用技术创新和技术知识扩散过程的三个模型的理论发展。第一个模型试图解释为什么大公司通常是第一个采用新的创新。另外两个模型处理信息传播中的摩擦，强调个人接触。研究的最后一部分涉及对多重均衡存在所引起的问题进行计量经济学调查。在这种情况下，偏好和技术的参数产生一组均衡，然后从这组均衡中选择一个结果。问题是如何估计马尔可夫过程的选择，因为部分运动的平衡将是由于外生冲击的存在。这项基础研究对技术冲击如何影响长期增长和周期性波动这一总体主题有着非常重要的意义。这项研究关注的技术冲击，是那些导致我们的知识储备永久增加的冲击。由于存量太大，任何人都不可能熟悉，因此其扩散将决定其对产出、生产率、投资和其他总量的影响。研究者的论点是，这种创新主要发生在企业层面，然后以一种尽管处于中心地位但仍未完全理解的方式传播到整个经济中。本课题已经完成的工作和计划开展的进一步工作构成了这一课题的前沿研究，在现代“内生增长”理论和现代经济周期理论中具有至关重要的意义。

The proposed research agenda consists of three broad parts. The first part involves a largely empirical investigation of the diffusion of technological innovations, and how this diffusion affects the aggregate behavior of output. More specifically, it is concerned with explaining the time-series behavior of GNP in terms of the time path of innovations and the speed with which they are diffused. This is expressed as a stochastic reduced- form equation relating current innovations in GNP to past innovations with various lags. Cross-section country data on GNP growth rates and innovation activity, for example, as measured by patent applications, are then used to estimate the parameters of the equation. The second part of the study consists of a theoretical development of three models regarding the adoption of technological innovations by firms, and of the process of diffusion of technical knowledge. The first of these models seeks to explain why bigger firms are usually the first to adopt a new innovation. The other two models deal with frictions in the spread of information, with an emphasis on personal contact. The final part of the research involves an econometric investigation of issues arising from the presence of multiple equilibria. In this setting, the parameters of preferences and technology generate a set of equilibria and then an outcome is chosen from this set. The question at issue is how to estimate the Markov process for selection given that part of the movement in equilibrium will be due to the presence of exogenous shocks. This fundamental research bears in a very important way on the general topic of how shocks to technology impact on both long- term growth and on cyclical fluctuations. The technological shocks, on which the research is focussed, are those that result in permanent additions to our stock of knowledge. Since the stock is much too large for anyone to be familiar with, its diffusion will determine its effect on output, productivity, investment, and other aggregates. It is the thesis of the investigator that such innovations occur largely at the firm level, and then spread throughout the economy in ways that despite their centrality are still imperfectly understood. Work already completed and the further work projected by this proposal, constitutes frontier research on the topic, which is of critical importance in the modern theory of "endogenous growth", and in modern business cycle theory.