The government can take action against negative externalities in three ways
- Property Rights: By establishing these rights, we can confront producers with the costs of their actions. This gives them incentive to change the quantity supplied.
Economically, firms realize their actions and external cost so their private MC curve becomes the MSC curve. - Taxes: If the government sets a tax equal to the external cost, then the firm will have to pay both the private marginal cost and tax. This leads to the firms supply to be the marginal social cost. In other words,
- Emission Charges: The government sets a price per unit of pollution. The more pollution the firm makes, the more emissions charges the firm must pay. This is an alternative to taxes.
- Cap-And-Trade: The government assigns a permit which tells you the cap (pollution quota) of the firm. Each permit may be different for each firm.
Note: firms trade permits until the marginal pollution cost is equal to the price of the permit.
Using Pollution Tax for Negative Externalities
Recall that the firms supply curve is the MPC curve.
We also have the demand curve MSD. When a pollution tax is implemented, we add the tax to the MPC curve. Thus, the firms supply curve is now
Since the tax is equal to the external cost, then we also notice that
Thus, the new market equilibrium is at the intersection of S1 and MSD curve.
How Government Regulates Positive Externalities
The government can take action against positive externalities in four ways:
- Public Production:: When the government implements public production, consumers realize the external benefits, thus changing their private MPB curve to the MSB curve. This achieves efficient market equilibrium
- Subsidies: a government payment that is made to producers. By adding subsidies, the firms supply curve becomes
- Vouchers: a token that is provided from the government and given to households. Consumer realizes the extra benefit gained from the token, and so the marginal private demand becomes the marginal social demand.
Since the product is cheaper to produce, firms produce more to compensate for the underproduction from external benefits.
Using Subsidies for Positive Externalities
Recall that the firms supply curve S0 is the MPC curve, and the demand curve is MPD.
Suppose MSC = MPC. When subsidy is implemented, we subtract the subsidy from the MPC. Thus, the firms supply curve is now
Thus, the new market equilibrium is at the intersection of S1 and MPD curve.