There's a thing in health insurance wonkdom call "churn." That's the regular flow of people in and out of insurance every year because of changes in their life status—stuff like losing or gaining a job, or a spouse. The individual market—the one that Obamacare primarily addresses—has always had a great deal of churn. That's one of the issues that made the Republican politicization of cancelled policies last fall such bullshit—these types of policies are cancelled pretty regularly, and the 1.9 million cancelled plans last fall were
well within the regular churn in the non-group market.
But Obamacare could change all that because of new rules preventing insurance companies from refusing people who have pre-existing conditions. As well, the subsidies will make keeping insurance more affordable, and because Medicaid is available for people who lose existing insurance and qualify—in the states that chose to expand.
People will still move between types of insurance, but fewer people should become uninsured, which will play a part in reducing the uninsured rate over time.
"There was churn everywhere in the health system," says Larry Levitt, a vice president at the Kaiser Family Foundation. "Some of that will still happen, but I think it will be minimized." […]
"It's too early to know how successful the ACA is going to be at reducing churn, because it depends a lot on people's behavior," Levitt said. "But there's the potential to change the culture of health insurance. It's possible that once we get people into the insurance system, they'll be less likely to leave when their circumstances change."
One of the reasons getting away from the employer-based insurance system is smart policy is because it could reduce churn, and could save costs for insurance companies in dealing with all the flux. There's always going to be some flux, as long as we have private health insurance, because people will shop around every enrollment period to see if they're going to get a better deal somewhere else, but it's still probably going to be reduced by the new law.