Moral hazard, monitoring costs, and optimal government intervention

When insurance firms can monitor with non-prohibitive costs the consumption of risk-influencing goods by an insured they have incentives to tax-subsidize the insured's consumption of the goods. If the government cannot monitor at a lower cost than private insurers, intervention is neither needed nor desirable. Where the government does have a monitoring-cost advantage, it cannot achieve a constrained optimum by commodity tax-subsidies alone. It must also augment the level of insurance and in some cases, prohibit private tax-subsidies by insurers. Such ''invasive'' intervention can be avoided if the government regulates the consumption of the risk-influencing goods.