The real effects of stock market mispricing at the aggregate: Theory and Empirical Evidence

In this paper we investigate whether stock market overpricing leads to aggregate (real) inefficiencies. We first investigate a standard dynamic contracting model of investment subject to financing constraints. We show that stock market mispricing will have two robust effects on welfare: on the one hand it will distort investment decisions and lead to inefficiencies. On the other hand it will alleviate underinvestment problems and allow some efficient projects to be undertaken. We then turn to the data and investigate which of the two effects dominates at the aggregate. By using proxies for investor sentiment within a vector autoregression (VAR) we find that positive shocks to sentiment boost (real) investment while reducing aggregate profits over the long run, all else equal. We interpret this as evidence that mispricing causes more inefficiencies than it corrects. JEL Codes: G0, E2