Capital-accumulation games under environmental regulation and duopolistic competition

In a differential game between two symmetric firms, provided with a clean and a dirty production activity, it is analyzed how investment and emissions are affected by environmental regulation. If both firms face the same environmental policy, a stricter policy reduces long-run investment in the dirty activity, while the impact on the clean activity is ambiguous. Both long-run emissions of each firm and total emissions decrease. This result does not necessarily hold if both firms face different policy instruments: Each firm's investment levels increase with a stricter environmental policy towards its rival, which causes more emissions by this firm.