We introduce a novel measure of corporate hierarchies for over 3,100 U.S. public firms. This measure is obtained from online resumes of 7 million employees and a network estimation technique that allows us to identify hierarchical layers. Equipped with this measure, we document several facts about corporate hierarchies. Firms have on average ten hierarchical layers and a pyramidal organizational structure. More hierarchical firms have a more educated workforce, higher internal promotion rates, and longer employee tenure. Their operating performance is higher, but they face higher administrative costs. They are more active acquirers and produce more patents, but not higher-quality patents. They exhibit lower stock return volatility and operating asset volatility. We also examine how companies adjust their hierarchies in response to demand and knowledge shocks. We find that pharmaceutical companies increased their number of layers following the Covid-19 pandemic, while companies flattened their hierarchies following the adoption of artificial intelligence (AI) technologies. These findings are consistent with the theoretical

predictions of existing models of corporate hierarchies.