We consider dynamic competition among platforms in a market with network externalities. A platform that dominated the market in the previous period becomes "focal" in the current period, in that agents play the equilibrium in which they adopt the focal platform whenever such equilibrium exists....

Modern economic theory predicts that tying can serve as a tool for leveraging market power. In line with this economic theory, competition authorities regulate the tying of Microsoft Windows with its Media Player or Internet browser in the EU and Japan. The authorities also take note of the...