Are monopolies economically efficient? Consider the market to the right. Compared to the perfectly competitive outcome, what would be the change in surplus if instead the market had one supplier that was a monopoly?

Deadweight loss (Triangle between all three lines, hits all three points).

Explanation:

This is explained to be triangle between all three lines as it hits all three points involved.

It can also be explained to be Harberger's triangle in the sense that the loss occurring in the trade of a good or service due to market power of buyers or sellers or a government intervention, or other bodies concerned is lost due when it is not produced maximumly to reach everyone who meeds it.

Deadweight loss, also can be a measure of lost economic efficiency when the socially optimal quantity of a good or a service is not produced. Non-optimal production can be caused by monopoly pricing in the case of artificial scarcity, a positive or negative externality, a tax or subsidy, or a binding price ceiling or price floor such as a minimum wage.