Asset Bubbles and Product Market Competition

This paper studies the interactions between asset bubbles and competition. I first document a negative industrylevel relationship between measures of stock market overvaluation and indicators of market power: larger overvaluation is associated with an increase in the number of firms, lower markups and a higher probability of negative earnings. I then construct multi-industry growth model featuring imperfect competition and rational bubbles that sheds light on these findings. By providing an entry or production subsidy, bubbles stimulate competition and reduce monopoly rents. When they are sufficiently large they can, however, lead to excessive entry and competition. I also show that imperfect competition depresses the interest rate, thereby relaxing the conditions for the emergence of rational bubbles.