This paper presents a political economy model where there is mutual feedback between investor protection and stock market development. Better investor protection induces companies to issue more equity and thereby leads to a broader stock market. In turn, equity issuance expands the shareholder base and increases support for shareholder protection. This feedback loop can generate multiple equilibria, with investor protection and stock market size being positively correlated across equilibria. The model's predictions are tested on panel data for 47 countries over 1993-2002, controlling for country and year effects and endogeneity issues. We also document international convergence in shareholder protection to best-practice standards, and show that it is correlated with cross-border M&A activity, consistent with the model.