Columbia经济系在国际经济学界的大名是响当当的了, Bhagwati、Stiglitz、Mundell等鼻祖级人物均在此地。附上两篇该系今年的JMP。


New products added by firms often share similarities with their existing products or connect with the firms in “intuitive” ways. We provide formal, empirical definitions of possible fundamentals underlying those connections and test them against one another in different industries to determine which matter more. To do this, we model additions of new products by firms using a dynamic model in which firms must pay a one-time startup cost for adding new products to their production line. We allow this cost to be reduced if the firm already produces similar products, or shares some characteristics with other firms already producing the product. We consider three measurable characteristics along which firms may be considered “close” to a particular product: input similarity, physical distance to existing locations of production, and upstream-downstream connectedness. We estimate the model using moment inequalities to compare the relative importance of the different proximity measures in each sector.


Recoveries from financial crises are characterized by low investment rates and declines in capital stocks. This paper constructs an equilibrium framework in which financial shocks have a persistent effect on aggregate investment. The key assumption is that physical capital is traded in a decentralized market with search frictions, generating ``capital unemployment.'' After a negative financial shock, the share of unemployed capital is high, and the economy dedicates more resources to absorbing existing unemployed capital into production, and less to accumulating new capital. An estimation of the model for the U.S. economy using Bayesian techniques shows that the model can generate the investment persistence and half of the output persistence observed in the Great Recession. Investment search frictions also lead to a different interpretation of the sources of business-cycle fluctuations, with a larger role for financial shocks, which account for 33% of output fluctuations. Extending the model to allow for heterogeneity in match productivity, the framework also provides a mechanism for procyclical capital reallocation, as observed in the data.

同系列，以前的帖子：
UC Davis 2014Job Market Paper
https://bbs.pinggu.org/thread-3495417-1-1.html

Yale 2014 Job Market Paper
https://bbs.pinggu.org/thread-3494168-1-1.html

Stanford 2014 Job Market Paper
https://bbs.pinggu.org/thread-3491842-1-1.html

Princeton 2014 Job Market Paper
https://bbs.pinggu.org/thread-3494070-1-1.html