And what about savings from moving away from "from fee-for-service design to providing stronger incentives to control costs or reward value"? In Elmendorf's view, "their precise effects are uncertain." He suggests testing options "to see whether they work as intended or to determine which design features work best." And maybe we should reform Medicare before we try to reshape the entire health care private sector. "Changes made in the Medicare program can also stimulate broader improvements in the health sector."

What about improved information technology? "Requiring that hospitals adopt electronic health records would reduce their costs for treating Medicare patients, but the program's payment rates would have to be reduced in order for the federal government to capture much of those savings." Preventive care? "Those efforts may still fail to generate net reductions in spending on health care because the number of people receiving the services is generally much larger than the number who would avoid expensive treatments as a result."

There are two more general problems, one of which Elmendorf spotlights: "Studies attribute the bulk of cost growth to the development of new treatments and other medical technologies," and so "reducing or slowing spending over the long term would probably require decreasing the pace of adopting new treatments and procedures or limiting the breadth of their application." If you pay less, you get less.

Second, and perhaps beyond the ambit of a data-driven CBO director, is the more general observation that the cost projections for government-run programs like Medicare and Medicare tend to come in low, while the cost projections for programs involving private-sector competition like the 2003 Medicare prescription drug benefit have turned out to be high.

Private-sector competition produces efficiencies and innovations that government bureaucracies almost never produce and can seldom keep up with. As Democrats scamper to reduce the projected costs of their health care bills, the rest of us might want to keep that in mind.