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....

In many retail settings such as fast-food chains, limited time “collect and win” games are often used to promote products and drive sales to the retail outlets. Unlike the more standard price discount or “buy-X-get-Y” promotional campaigns, the “collect and win” games create short...