Health insurance which provides protection against the high cost of treating severe or lengthy illnesses or disabilities. Generally such policies cover all or a specified percentage of medical expenses above an amount that is the responsibility of the insured himself (or the responsibility of another insurance policy up to a maximum limit of liability). Under pending NHI proposals of this type, protection would typically begin after an individual or family unit had incurred medical expenses equal to a specified dollar amount (e.g., $2,000 within a 12-month period) or a specified percentage of income (e.g., fifteen percent); or had been in a medical institution for a specified period (e.g., 60 days). Individuals would be liable for all costs up to the specified limits. However, in the absence of any effective prohibition against doing so, they could be expected to obtain health insurance protection for costs below the catastrophic limits. Generally there is no maximum amount of coverage under these plans; however, many include some coinsurance.