National health insurance plans provide millions of people worldwide with health insurance, and it is paid for differently in different countries. For example, in a single-payer system of national health insurance, the government heavily subsidizes health care by substantially raising taxes on the nation. By contrast, the U.S. has a mixed health care system, where there are both public and private health insurance plans. Americans of retirement age and others too poor to afford health insurance benefit from Medicare and Medicaid, while those who are excluded from those criteria purchase private health insurance plans.
National health insurance is a way of pooling health risks together, thereby minimizing the fees accruing to the people that are the most sick. Think of it this way: sick people are most in need of health insurance, yet insurance companies have the least incentive to provide health insurance to those people at an affordable rate. Along the same but opposite lines, healthy people have less incentive to purchase health insurance, because it is not clear that they will need it. Thus, without a national health insurance plan, the people that need health insurance the most have the greatest difficulty finding affordable care. By grouping everyone together, the insurance pool bears less risk per individual, which makes it more affordable for those that need it most.
Believe it or not, a national health insurance plan may have less bureaucracy than a set of privately-provided plans, drastically decreasing the overall cost of health insurance for the average individual. Doctors Steffie Woolhander and David Himmelstein argue that "Reducing our [the United States's] bureaucratic apparatus to Canadian levels would save 10% to 15% of current health care spending, at least $120 billion annually, enough to fully cover the uninsured and upgrade coverage for those now underinsured."
Though a national health insurance plan occasionally comes with some harms, such as long lines for very important procedures, the average person greatly benefits from having access to regular visits to quality doctors and affordable prescription drugs. According to the Economist Intelligence Unit's Quality-of-Life Index, there is a high correlation between a country having socialized medicine and a person having a higher overall quality of life. In a comparison between two otherwise similar countries (e.g. Western European countries and the United States), countries with national health insurance also have higher life expectancies and are rated as having a higher quality of health care overall.