has details:

Romney, the former Massachusetts governor, said that was “simply impossible” that free riders had gone up, because the percentage of insured residents had increased under the law to 98 percent.

Romney is right. The percentage of insured residents in the state went up from 93.6 percent in 2006, the year the law was enacted, to 98.1 percent in 2010. And data from the state Division of Health Care Finance and Policy show a 46 percent decline in the number of free care medical visits paid for by the state’s Health Care Safety Net. The number of inpatient discharges and outpatient visits under the program went from 2.1 million in 2006 to 1.1 million in 2010 (see page 12).

Contradicting Santorum’s claim, the Blue Cross Blue Shield of Massachusetts Foundation said in a November report that usage of the state’s free care, or safety net, “fell dramatically, as expected” after the law took effect.

BSBC Foundation report, Nov. 2011: In fact, the number of HSN patient visits at hospitals and community health centers declined by 36 percent in the first full HSN fiscal year of health reform. Over the past three years, HSN utilization has trended upward but is still below pre-reform levels.

A Santorum campaign spokesman pointed us to a Wall Street Journal column by Michael F. Cannon of the libertarian Cato Institute, who stated that “Massachusetts reported a nearly fivefold increase in such free riding after its mandate took effect.” But that doesn’t square with official data just cited. Cannon didn’t specify the time period and so may have referred to some temporary or transitory bump in free riders. We will update this item if we are able to get more information from Cannon.Santorum blamed the supposed increase in free riders on persons choosing to pay the penalty instead of buying insurance. But that doesn’t square with official state data either. In 2009, only 48,000 residents paid a penalty — 26,000 of them were uninsured for the entire year, and 22,000 for part of the year, according to state figures. Those aren’t big numbers compared with the usage numbers for the Health Care Safety Net — 1.1 million payments in 2010. The evidence doesn’t suggest that those penalty-payers are driving an increase — let alone a “fivefold” one — in reliance on free care.

In fact, one of the issues with costs has been that employers were willing to adopt plans to cover their employees, resulting in less revenue from penalties for not insuring them. The number of insureds covered in Massachusetts has increased each year, and Romney's numbers are correct -- there are not 5 times the number of 'free-riders', though there are indeed some who gamed the system by paying the penalty, getting insurance, paying for a few months while they received the care they needed and then dropped it. This was largely overcome as the penalties for not having insurance increased from 2008-2010. This Boston Globe article is a good summary of what has worked well and what has had some bumpy patches over its 5-year implementation.

ROMNEY: Secondly, 98 percent of the people have insurance. And so the idea that more people are free-riding the system is simply impossible. Half of those people got insurance on their own. Others got help in buying the insurance.

ROMNEY: Excuse me, but I just must preface the next part with a bit of another interruption. We are now about to witness the "other Mitt Romney". The one who hates Obama's identical plan that hands off exchanges to the states and gives them extra Medicaid dollars. The one who parrots baloney claims about cutting Medicare rather than telling the truth about the $500 billion representing the bonus insurers received for privatizing Medicare in certain areas. He's about to flip to his own flop.

Look, I know you don't like the plan that we had. I don't like the Obama plan. His plan cuts Medicare by $500 billion. We didn't, of course, touch anything like that. He raises taxes by $500 billion. We didn't do that.

He wasn't interested in the 8 percent of the people that were uninsured. He was concerned about the 100 percent of the people of the country. "Obama-care" takes over health care for the American people.

If I'm president of the United States, I will stop it. And in debating Barack Obama, I will be able to show that I have passion and concern for the people in this country that need health care, like this young woman who asked the question.

But I will be able to point out that what he did was wrong. It was bad medicine, it's bad for the economy, and I will repeal it.

If I ever meet Mitt Romney, I will look forward to getting a lesson from him on how to talk out of both sides of my mouth while flipping back and forth like a fish in a frying pan. It's quite a gift he has.