Aggregate fluctuations and the network structure of intersectoral trade

This paper analyzes the flow of intermediate inputs across sectors by adopting a network perspective on sectoral interactions. I apply these tools to show how fluctuations in aggregate economic activity can be obtained from independent shocks to individual sectors. First, I characterize the network structure of input trade in the U.S. On the demand side, a typical sector relies on a small number of key inputs and sectors are homogeneous in this respect. However, in their role as input-suppliers sectors do differ: many specialized input suppliers coexist alongside general purpose sectors functioning as hubs to the economy. I then develop a model of intersectoral linkages that can reproduce these connectivity features. In a standard multisector setup, I use this model to provide analytical expressions linking aggregate volatility to the network structure of input trade. I show that the presence of sectoral hubs - by coupling production decisions across sectors - leads to fluctuations in aggregates.