With one-way spillovers, the standard symmetric two-period R&D model leads to an asymmetric equilibrium only, with endogenous innovator and imitator. We show how R&D decisions and measures of firm heterogeneity - market shares, R&D shares, and profits - depend on spillovers and on R&D costs....

For Bertrand duopoly with linear costs, we establish via a single (counter-)example that: (i) A new monotone transformation of the firms' profit functions may lead to the supermodularity of transformed profits when the standard log and identity transformations both fail to do so, and (ii)...

This note relates to Topkis (1995). We establish via counterexample that:(i) A new monotone transformation of the firms' profit functions may lead to cardinal complementarity when the standard log and identity transformations both fail, and (ii) Topkis's notion of critical sufficient condition...

An infinite-horizon, stochastic model of entry and exit with sunk costs and imperfect competition is constructed. Simple examples provide insights into: (1) the relationship between sunk costs and industry concentration, (2) entry when current profits are negative, and (3) the relationship...

We provide an extensive comparison of the R&D models of d'Aspremont-Jacquemin (1988) and Kamien-Muller-Zang (1992), exposing full or partial conflict in key conclusions and policy prescriptions. Using three separate formal and/or intuitive criteria, we argue that the first model is invalid for...