Understanding what determines firm boundaries and the choice between interacting in a firm or a market is not only the fundamental concern of the theory of the firm, but it is also one of the most important issues in economics. Data on value added, for example, reveal that in the US,...

I discuss the use of simulation techniques to evaluate unilateral effects of horizontal mergers and the pitfalls that one can encounter when using them. Simple econometric models are desirable because they can be implemented in a short period of time and can be understood by non experts....