重要な公共財

Private firms cannot exclude non-payers from consuming public goods, creating a free rider problem. Since they cannot prevent people from benefiting without paying, insufficient profit exists to justify production. Even when the total value to society exceeds production costs, private companies lack economic incentive to provide these goods at socially efficient quantities.

National defense protects all residents equally from external threats, and no one can be excluded from its protection once established. Every citizen benefits regardless of whether they pay taxes, making it non-excludable and non-rivalrous. Only government can collect payment from everyone through taxes to fund this essential service.

Basic research generates general knowledge like mathematical theorems or physics principles that cannot be owned or patented by a single party. Private firms have little incentive to fund basic research because its outcomes cannot be easily monetized. Governments fund basic research because it contributes to society's general knowledge pool, benefiting everyone.

Law and order, including policing and judicial systems, benefits all citizens equally by ensuring safety and societal stability. These services cannot exclude individuals from protection, and one person's benefit does not reduce availability for others. Government provision prevents exclusion and ensures impartial enforcement across the entire population.

Public goods are non-excludable, meaning people cannot be prevented from using them, and non-rivalrous, meaning one person's use does not reduce availability for others. These characteristics prevent private markets from supplying them efficiently because firms cannot collect payment from all beneficiaries. The optimal level of public goods requires government intervention to ensure socially efficient provision.

Public goods are funded through taxes collected from individuals and businesses. These tax revenues enable governments to provide essential services that benefit entire society but would not be supplied by private markets. Tax funding ensures that all citizens contribute to and benefit from public goods like national defense, basic research, and street lighting.

Street lighting benefits everyone in an area by improving visibility and safety at night. It is impractical to charge individuals for using public streetlights, making it impossible for private firms to collect payment from all beneficiaries. Government provision through tax funding ensures universal access to this non-excludable, non-rivalrous service.