Chapter 1 analyzes firms' incentives to collude in timing of introducing new product models in the framework of a repeated game of preemption and how the time intervals between introductions of new models could vary across different economies. For a given interest rate, sustainable time intervals exist only when consumers' demand grows sufficiently large over time. When the Pareto superior time interval is sustainable, it becomes longer as the number of firms increases, the cost of R&D rises, the cost of production rises, or market demand size at each moment shrinks proportionately. I also characterize the set of collusive subgame perfect equilibrium values and collusive subgame perfect equilibrium strategies. Chapter 2 models a trade-of...