A maximum price for a good is established below market equilibrium. This will cause disequilibrium - shortage of goods.
Floor Prices
Set prices above the market equilibrium price as a minimum price that must be paid. They result in excess supply.
Externalities
A side effect or consequence of an activity that is not reflected in the cost of that activity.
Negative Externalities
Pollution
Environmental damage
Positive Externalities
Parks
Museums
Galleries
Merit Goods
Not produced in sufficient quantity by private sector because insufficient value is placed on these goods or the market is too small. Private sector firms are unable to achieve profit maximisation so they do not produce these goods.
Public Goods
Goods private firms are unwilling to supply since usage cannot be restricted to those willing to pay for the good. They are non-exclusive and non-rival.
Market Failure
When markets do not produce desired outcomes.
Market price may be too high or low
Equilibrium quantity may be too high or low
When this occurs, governments may intervene in the market.
Positive Externalities

When consuming or producing a good causes a benefit to a third party
Negative Externalities

When consuming or producing a good causes a cost to a third party.
Tax
Governments can implement laws to restrict production levels if private organisations do not consider negative externalities. Governments may also tax businesses to reduce production levels with increased production costs.
Subsidies

Subsidies may be granted to producers that have positive externalities. They keep production costs or prices of goods lower.