The CPI focuses mainly on out-of-pocket health-care costs, being an index of what consumers themselves are paying. The Fed's preferred gauge, the price index for personal consumption expenditures (PCE) covers "all goods and services consumed by households regardless of who paid for them," or even if there was any explicit payment, as Morgan Stanley puts it.
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That means health-care services make up roughly 20 percent of core PCE, because they cover the consumption of health care paid for by somebody else—namely, by Medicare, Medicaid and employers. By contrast, health-care services account for only about 8 percent of the core CPI.
(The "core" readings for each index simply strip out food and energy prices, which are notably volatile, to better gauge underlying prices pressures across the economy.)
The total price of providing Americans health care, then, is best reflected in the PCE, and has actually been putting downward pressure on that index for years now. It's also driven that yawning gap between the super-low PCE readings and the higher CPI ones.
Downward pressure? Indeed, owing in large part to hefty cuts in Medicare payments that go back to the 2010 implementation of the Affordable Care Act, or "Obamacare."
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Since then, "the government has reduced payments to Medicare Advantage plans by nearly 15 percent," said Cantor Fitzgerald analyst Joseph France. Medicare Advantage refers to the administration of Medicare payments through private health insurers.
The effect on the Fed's preferred inflation gauge has been especially large.
Core PCE services inflation, in fact, "has been stable for several years in a 2% to 2.5% range," if health care is excluded, according to Morgan Stanley. The March reading, by that metric, was up 2.3 percent from a year earlier, the firm calculates—comfortably above the Fed's targeted 1.5 to 2 percent range for core goods and services inflation.
Enter Humana, which The Wall Street Journal last month reported is exploring a sale to one of its rivals, and "is seen as a prize because of its powerful Medicare franchise."
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Humana is the second largest provider of Medicare Advantage plans, with about 3.2 million enrollees (as of April 1 payment data), according to Stifel Nicolaus & Co. The largest is UnitedHealth, with just under 3.5 million.
Surprisingly, these Medicare giants have weathered the enormous payment cuts relatively well. Humana even managed to increase its key profit margin in the first half of 2010 when the first major cuts hit, said Stifel analyst Thomas Carroll. The sheer number of Americans hitting age 65 and enrolling in plans has helped to offset the government's payment cuts.
And now, a bright spot for big insurers may be at hand: a major inflection point with regard to Medicare payments.
"In 2016, we're expecting to see the first positive rate increase for Medicare Advantage for the players like Humana that we've seen in years," Carroll said last month on CNBC's "Closing Bell."