The debate over how to structure health insurance in the United States returns, periodically, to an analogy that sounds intuitive on the surface: why not make health insurance work like car insurance? Individuals bear responsibility for their own coverage, prices vary based on risk, and the market — not the government — determines what products are available and at what price.

The analogy appeals to those who are skeptical of government involvement in healthcare and who believe market mechanisms are more efficient allocators of resources than centralized planning. It also resonates with a cultural emphasis on personal responsibility: if you drive recklessly, you pay more for car insurance; shouldn't the same principle apply to health choices?

But the analogy breaks down in important ways that health economists have extensively documented.

First, car ownership is optional. Healthcare consumption is not — the human body inevitably requires medical attention, regardless of individual choices. You can opt out of driving and therefore opt out of car insurance. You cannot opt out of having a body.

Second, the risk profiles are fundamentally different. Car insurance primarily covers accidents — events that are, by definition, unpredictable and at least partly within individual control. Most healthcare costs arise from conditions that are largely outside individual control: genetic predispositions, the random distribution of disease, aging. The moral logic of risk-based pricing that applies to driving does not map cleanly onto illness.

Third, adverse selection dynamics in health insurance markets — where sick people are more likely to seek coverage, driving up premiums for everyone, which causes healthy people to drop coverage, which drives premiums higher still — produce market failures that don't have clear car insurance parallels.

What works for auto coverage and what works for health coverage are shaped by fundamentally different underlying realities. The analogy makes for an appealing rhetorical frame and a poor policy model.