We show that corporate financial policies are highly interdependent; firms make financing decisions in large part by responding to the financing decisions of their peers, as opposed to changes in firm-specific characteristics. On average, a one standard deviation change in peer firms' leverage...

Unregulated US corporations dramatically increased their debt usage over the past century. Aggregate leverage — low and stable before 1945 — more than tripled between 1945 and 1970 from 11% to 35%, eventually reaching 47% by the early 1990s. The median firm in 1946 had no debt, but by 1970...