​This book provides an updated overview of the recent progress in the theoretical study of third-degree price discrimination. It is a marketing tactic and is said to be present if the unit price is different across different groups of buyers. Its welfare evaluation is often difficult because it entails two countervailing effects: on one hand, it exploits surplus from consumers who have high willingness-to-pay, but on the other hand, it generates gains from trade from consumers who otherwise would not purchase the good. Recognizing this difficulty, we provide new insights on evaluation of...