"If something cannot go on forever, it will stop."
* Stein's Law, after economist Herbert Stein (1916-1999)
WASHINGTON - We all know that Stein's Law will someday apply to health care spending, which has risen from 5 percent of the economy (gross domestic product) in 1960 to almost 18 percent now.
What we don't know is how and when its share of the economy will stabilize.
Will this result from spending controls imposed by Washington; from delivery system "reforms" that spontaneously cut "waste"; from rationing, which limits spending by denying people treatment; or by some combination of these?
As for when, could it be now?
Evidence of a spending slowdown is overwhelming. From 2009 to 2011, health spending remained at 17.9 percent of GDP, and actuaries at the Centers for Medicare and Medicaid Services predict it will stay there in 2012 (final figures aren't in) and 2013.
If continued, this would have huge implications for the federal budget. Harvard economist David Cutler estimates the next decade's savings at $770 billion.
Health care's stranglehold on other national priorities would loosen. Cutler is among those who think this is possible.
Writing in the journal Health Affairs - whose latest issue is devoted to costs - he and economist Nikhil Sahni argue that the slower spending reflects, at least partially, permanent changes.
Drug costs are abating because there are "fewer new blockbusters," and more drugs are "coming off patent" and can be replaced by cheaper generics.
Hospitals are growing more efficient; since 2001, the University of Pittsburgh Medical Center has "reduced its rate of hospital-acquired infections by 85 percent," they report.
More cost-sharing (higher deductibles and co-payments) has curbed use, they say.
Cutler's optimism isn't universal. A study by the nonpartisan Kaiser Family Foundation and the Center for Sustainable Health Spending attributes 77 percent of the spending slowdown to the Great Recession, the weak recovery and low inflation.
People lose private insurance; their health spending falls, though it doesn't disappear. Even those with insurance are more careful about out-of-pocket costs.
In 2011, both hospital admissions and the number of filled drug prescriptions declined slightly, reports the Health Care Cost Institute.
By this view, a stronger economy will cause health spending to reaccelerate.
Another skeptic is Paul Hewitt, research director for the Council for Affordable Health Coverage. He says that 70 percent to 80 percent of hospitals' and physicians' office costs are labor: all the doctors, nurses, administrators, aides and clerical workers.