Economics
Consumer Surplus and Producer Surplus Measurement
Quick fact
The sum of consumer and producer surplus is called 'total surplus,' and economists use it to judge whether a market is efficient—the 'invisible hand' maximizes this total at the free-market equilibrium.
Why this is interesting
You just paid $3 for your morning coffee, but you would have paid $5 for it—what happens to that extra $2? And how much does the café actually gain from selling to you?