"No one would have predicted this slowdown four years ago," said the center's president, Robert Greenstein, adding that no one understands why it happened.
Until policymakers figure out what is happening, he said, it would be difficult to figure out the best way to continue to bring costs down.
"We know we have to do more on health care," Greenstein said. "But we're not in a position now to make intelligent policy choices."
Other economists warn that putting off action to address the longer-term problem of funding entitlements for an aging population could make them even more difficult to solve. In his address, Obama mentioned the need for entitlement reform, but offered no major proposals for achieving it.
"A cynical reading is [Obama] can skate by and leave his successor with a disaster," said Douglas Holtz-Eakin, a former CBO director who now heads the American Action Forum, a conservative think tank. "We've made zero progress on the structural problem, and they just don't want to do it."