If you're feeling health care wonky, here's actual statistics as to how much a mandate could save:

So the Obama plan would leave more people uninsured than the Clinton plan. How big is the difference?

To answer this question you need to make a detailed analysis of health care decisions. That's what Jonathan Gruber of M.I.T., one of America's leading health care economists, does in a new paper.

Mr. Gruber finds that a plan without mandates, broadly resembling the Obama plan, would cover 23 million of those currently uninsured, at a taxpayer cost of $102 billion per year. An otherwise identical plan with mandates would cover 45 million of the uninsured -- essentially everyone -- at a taxpayer cost of $124 billion. Over all, the Obama-type plan would cost $4,400 per newly insured person, the Clinton-type plan only $2,700.

That doesn't look like a trivial difference to me. One plan achieves more or less universal coverage; the other, although it costs more than 80 percent as much, covers only about half of those currently uninsured.

It saves money because:

Why have a mandate? The whole point of a universal health insurance system is that everyone pays in, even if they're currently healthy, and in return everyone has insurance coverage if and when they need it.

And it's not just a matter of principle. As a practical matter, letting people opt out if they don't feel like buying insurance would make insurance substantially more expensive for everyone else.

Here's why: under the Obama plan, as it now stands, healthy people could choose not to buy insurance -- then sign up for it if they developed health problems later. Insurance companies couldn't turn them away, because Mr. Obama's plan, like those of his rivals, requires that insurers offer the same policy to everyone.

As a result, people who did the right thing and bought insurance when they were healthy would end up subsidizing those who didn't sign up for insurance until or unless they needed medical care.

Both those quotations come from Nobel-winning economist Paul Krugman, who's also something of a health care policy wonk. The point of health insurance or a health care system is that people who are healthy pay into the system to reduce costs for the people who are sick. They do so in case they become sick themselves.

But if costs are too high, or if they're feeling lucky (which a lot of people who are healthy do), then they don't buy insurance. Which means that there's a higher percentage of sick people in the health care system than there needs to be, and the costs for that group go up.

And they still end up paying for those folks who thought they were healthy or could afford insurance, because those people, if something happens or if they ignore a developing condition, end up in the ER, the absolutely most expensive and inefficient way to handle patients. The costs of their health care are passed on to everyone else if they can't pay, and often those folks go bankrupt, passing along the costs of their health care, again, to everyone else who bought insurance in the first place.

So, yeah, this is a big deal. Especially since many people just don't like the idea of a mandate; "Don't infringe on my rights," Ayn Rand, and "Don't force people to buy something!" are much easier to understand than Jonathan Gruber's number-crunching. Plus the traditional media is against universal health care, which means that we're fighting an uphill battle.

One other thing. If you're feeling wonky, then go read this old piece from Ezra Klein about health care systems around the world to get an idea of what the US could be doing. We shouldn't be talking "health care reform" vs. "no health care reform," or even "universal health care" vs. "no universal health care," especially when there are so many details to work out.