We argue that the network of investment production and purchases across sectors is an important propagation mechanism for understanding business cycles. Empirically, we show that the majority of investment goods are produced by a few “investment hubs” which are more cyclical than other sectors. We embed this investment network into a multisector business cycle model and show that sector-specific shocks to the investment hubs and their key suppliers have large effects on aggregate employment and drive down labor productivity. Quantitatively, we find that sector-specific shocks to hubs and their suppliers account for an increasing share of aggregate fluctuations over time, generating the declining cyclicality of labor productivity and other changes in business cycle patterns since the 1980s.

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投资网络，部门联动和不断变化的美国经济周期

我们认为跨部门的投资生产和购买网络是理解商业周期的重要传播机制。根据经验，我们表明，大多数投资商品是由一些“投资中心”生产的，这些“投资中心”的周期性比其他部门要高。我们将此投资网络嵌入到多部门商业周期模型中，并表明对投资中心及其主要供应商的特定行业冲击会对总就业产生重大影响，并降低劳动生产率。从数量上看，我们发现，随着时间的流逝，枢纽及其供应商遭受的特定行业冲击在总波动中所占的份额越来越大，导致劳动生产率的周期性下降以及自1980年代以来商业周期模式的其他变化。