This tax should be equal to the marginal societal damage at the point of optimality, which implies that it is also equal to the marginal private benefit at that point. In a world with no further disturbances, this would force a profit-maximising producer to restrict his emissions exactly at the optimal point. Governments, in the interest of maximising the total welfare of society, act here as the caretakers of social resources and set the socially optimal price. The incentive for the producer to reduce his emissions is now the price he has to pay for emitting sparks, particulates or greenhouse gases.