身边的经济学·社会常识英语30篇（1）

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为什么公共品难以由市场供给

Public goods are non-excludable and non-rivalrous, making private profit difficult to capture.
Once a lighthouse shines, ships cannot be charged individually for its light.
Firms avoid investing in such goods because users can benefit without paying—the free-rider problem.
National defense, clean air, and street lighting all share these traits.
Markets underproduce them unless governments step in with funding or regulation.
Voluntary contributions rarely cover full costs due to coordination and trust issues.
Even digital public goods like open-source software rely on subsidies or donations.
Local governments often fund parks and libraries because their benefits spill across neighborhoods.
Assigning property rights to clean rivers or stable climate remains legally and technically complex.
Thus, public provision fills gaps where markets naturally stall or fail.