Key Idea: Topic 2.8 explains why markets fail when there are external costs or benefits that are not reflected in the price. It covers negative externalities, positive externalities, and common pool resources.
✅ Core definitions
📉 Negative externalities
📈 Positive externalities
🌊 Common pool resources
Know the diagram labels: MPC, MSC, MPB, MSB. The gap between private and social curves = the externality. The welfare loss is ALWAYS a triangle.