Health insurance is an insurance that covers the whole or a part of the risk of a person incurring medical expenses, spreading the risk over a large number of persons. By estimating the overall risk of health care and health system expenses over the risk pool, an insurer can develop a routine finance structure, such as a monthly premium or payroll tax, to provide the money to pay for the health care benefits specified in the insurance agreement.[1] The benefit is administered by a central organization such as a government agency, private business, or not-for-profit entity.
^ Bump, Jesse B. (19 October 2010). "The long road to universal health coverage. A century of lessons for development strategy" (PDF). Seattle: PATH. Retrieved 10 March 2013. Carrin and James have identified 1988—105 years after Bismarck's first sickness fund laws—as the date Germany achieved universal health coverage through this series of extensions to minimum benefit packages and expansions of the enrolled population. Bärnighausen and Sauerborn have quantified this long-term progressive increase in the proportion of the German population covered by public and private insurance. Their graph is reproduced below as Figure 1: German Population Enrolled in Health Insurance (%) 1885–1995.
Health insurance isn’t just about access to healthcare – it’s also about protection from financial ruin. Insurance can be expensive, but lacking coverage can cost much more. No one is invincible; anybody can be injured in a car accident, or receive an unexpected diagnosis. While it’s unclear whether poor health begets financial insecurity or vice versa, the correlation between not having health insurance and financial instability is indisputable. Indeed, medical debt is the leading cause of personal bankruptcy filings among Americans.
Out-of-pocket maximum: Similar to coverage limits, except that in this case, the insured person's payment obligation ends when they reach the out-of-pocket maximum, and health insurance pays all further covered costs. Out-of-pocket maximum can be limited to a specific benefit category (such as prescription drugs) or can apply to all coverage provided during a specific benefit year.

The share of Americans without health insurance has been cut in half since 2013. Many of the reforms instituted by the Affordable Care Act of 2010 were designed to extend health care coverage to those without it; however, high cost growth continues unabated.[3] National health expenditures are projected to grow 4.7% per person per year from 2016 to 2025. Public healthcare spending was 29% of federal mandated spending in 1990 and 35% of it in 2000. It is also projected to be roughly half in 2025.[4]