Forty-seven million Americans are without health insurance, according to the 2007 U.S. Census. The Kaiser Family Foundation says average American family spends $12,106 on health care each year. 

Hardly surprising then that "fixing" the U.S. health care system is one of the biggest concerns among voters in this presidential election year, and the elusive goal seems to be something called "universal health care." 

But what does "universal health care" really mean?

The answer isn't simple, according to Rachel DeGolia, executive director for the Universal Health Care Action Network, an activist group. 

"The term gets bandied about, but no one knows what it means because it doesn't define a plan. It defines the type of care people are looking for," DeGolia said. To simplify the concept, people should think of universal health care in the same way they think of universal police protection, she said.

The details of the many universal health care plans proposed over the years differ, but they all seek to accomplish the following: getting more people covered while saving money over time.

Presumptive Democratic presidential candidate Sen. Barack Obama has proposed a plan that offers income-based federal subsidies to middle-class families who don't have employer-based plans and who also don’t qualify for Medicaid. The model is based on one proposed by Yale political scientist Jacob Hacker, and allows Americans with insurance to keep their plans while offering government-sanctioned options to those who cannot afford it.

"In other words, [the U.S.] would keep the private insurance market, but would create mechanisms for all people to purchase insurance," said Flavio Casoy, policy chairperson for the American Medical Students Association, a student group for physicians in training.

Under the Obama plan, parents would be required by law to have children covered from birth either through their employer-sponsored plan, Medicaid, or options offered by the government. People of all ages, even those with pre-existing medical conditions, would be guaranteed coverage under this plan.

Funds to pay for this type of plan would likely have to be raised by tax dollars, according to Jonathan Cohn, author of Sick: The Untold Story of America's Health Care Crisis and the People who Pay the Price.

"It might require that everyone pays more in taxes. And even though those same people will be saving money in their private insurance, people only hear 'taxes,' and they get stuck on that. It's not going to be easy," Cohn said. 

Another type of plan not supported by either presidential candidate-- yet often explored by academics and policy makers -- would create from scratch a government-run health care system. Under this centralized plan, the government would operate a health care system directly just like it does Medicaid, the federally funded insurance program for the poor, according to Casoy. With this model, the government could choose to contract with a nonprofit agency to provide insurance and health care services. This plan most closely matches the health care system found in the United Kingdom, the United Health Service. 

Of course, not everyone likes the idea of the government running the health care system, and the plan proposed by likely Republican presidential candidate Sen.John McCain addresses that concern.

Under McCain’s plan, Americans would shop for their own personalized coverage, and employer-sponsored insurance would be abolished. Annual tax credits totaling $2,500 for individuals and $5,000 for families would be given to help offset the cost of insurance expenses. Ideally, this plan would create competition in the insurance marketplace and lower insurance prices for all.

However, concerns have risen with the concept of abolishing employer-provided insurance. "You can't tear down the employer system without building something new in its place," said Cohn. "Universal health care is a guarantee of insurance for everybody, and doing so inevitably involves getting the government involved."

Cohn said financial concerns will be an impediment to any proposal. From the time a plan is put into action, it would likely be 10 years or more before the U.S. began to save money.

In addition, the sheer number of Americans could present a road block, according to Michael Tanner of the Cato Institute and author of a study, The Grass is Not Always Greener: A Look at National Health Care Systems Around the World.

"If health care in this country is going to be universal, there's the matter of tracking people down to give it to them," Tanner said. "How do you track down every homeless and mentally ill person? The concept that you could get a piece of paper into everyone's hand is ridiculous."

Tanner said the U.S. should make efforts to get as many people covered as possible, but recognize that it's always going to be a work in progress. Even in countries that do have a universal plan, like France and Germany, 1% or 2% of the population exists under the radar, according to the Cato Institute. However, Tanner agreed that those numbers are far better than the 15% of Americans estimated to be without coverage.

Although there is no widely accepted standard for universal health care and the proposals of McCain and Obama differ widely, both candidates have made cost control an important piece of their health care platforms, Tanner said. No matter the election's outcome, Republicans and Democrats both agree that people need access to quality, affordable healthcare.

"Both candidates have options in place that will facilitate better coverage for more people, and if we can do that then we can say healthcare has improved in this country," he said.