A lighthouse warns every ship at sea. It is expensive to build and maintain, but once it is shining, no captain can be excluded from its beam. Some shipowners might refuse to pay for it, hoping others will cover the cost. Those are free riders, people who benefit from a good without contributing to it.

Free riding is a problem for public goods, which are non-excludable and non-rivalrous. National defense, clean air, public radio, and basic research all suffer from it. If everyone waits for someone else to pay, the good gets underprovided or not provided at all. That is why governments step in, funding these goods through taxes rather than voluntary contributions.

Free riding is not always about money. In a team project, one member may slack off while others do the work. In international climate negotiations, countries may hesitate to cut emissions if they believe others will do it for them. The logic is the same: private incentive diverges from collective interest. Solving it requires institutions that align the two, whether through taxes, regulation, or social norms.

Classic examples

• National defense
• Public broadcasting
• Clean air and water
• Basic scientific research
• International climate agreements