President Barack Obama has declared that his goal in health care reform is “expanding coverage to all Americans.” So what’s the price tag on universal coverage?

Some reformers are throwing around numbers like $1 trillion or $1.5 trillion. But according to the Urban Institute, the cost would be closer to $2 trillion.

Jack Hadley and his colleagues estimate, “If all uninsured people were fully covered [in 2008], their medical spending would increase by $122.6 billion.” If we assume that the cost of covering the uninsured will grow at the same rate the federal government assumes for all health spending growth (6.2 percent), then from 2010 through 2019, the cost of covering the uninsured would be $1.8 trillion.

That’s at a minimum. According to Hadley et al., their estimate “is neither the cost of a specific plan nor necessarily the same as the government’s costs, which could be higher, depending on plans’ financing structures and the extent of crowd-out.” Crowd-out is like collateral damange. When you’re dropping money from the sky, some will inevitably strike innocent bystanders (i.e., the insured). To ensure you hit the uninsured with $122.6 billion, you need to drop a lot more than that amount.

Thus the full cost of covering the uninsured would be closer to — and possibly well over — $2 trillion.