Final answer:
Deadweight loss is the reduction in total surplus due to inefficient market outcomes, often caused by price controls, as seen in the area labeled U + W on a supply and demand graph.
Step-by-step explanation:
The term deadweight loss refers to the loss in social surplus that occurs when an economy produces at an inefficient quantity due to various reasons such as price controls, taxes, subsidies, or monopolies. This can be visualized on a supply and demand graph where the deadweight loss is typically represented by a triangle formed by the supply and demand curves and the quantity traded. In the context given, where 80 units of goods are traded, if a price control is blocking some suppliers and demanders from transactions they would both be willing to make, the deadweight loss is illustrated as the area labeled U + W. This area represents the lost gains from trade or the value of wasted resources that could have been traded if the market were operating at an efficient level.