Romney adviser Glenn Hubbard’s op-ed in yesterday’s Wall Street Journal has already attracted plenty of criticism from the White House and liberal pundits for his claim that President Obama’s budget would require “an across-the-board tax increase of 11% for taxpayers with incomes under $200,000.” Austan Goolsbee, Ezra Klein and others have already responded to this argument, but there’s another misleading part in the op-ed that’s also worth rebutting:

The Congressional Budget Office estimates that, absent changes in policy, the nation will spend 10 percentage points of GDP more on Social Security, Medicare, Medicaid and related programs in 2058 than it does today.

The math is correct, but Hubbard leaves out the breakdown of said growth. This year, says the CBO, Social Security will consume 4.8 percent of GDP, while Medicare, Medicaid and related programs will consume 5.3 percent. In 2058, Social Security will consume 6 percent of GDP (a 25 percent increase), while the health-care programs will have more than doubled to 13 percent (a 145 percent increase). In addition, in those same projections, Social Security holds steady between 5.9 and 6.1 percent of GDP for thirty years prior to 2058.

The point here (and it’s one that many have made before) is that it’s important to distinguish the problems facing these two sets of entitlements. Medicare, Medicaid, et. al. face a real funding problem, thanks not only to demography but also (perhaps even mostly) to ever-rising health-care costs. Social Security, though, as the CBO has shown, can extend its trust fund exhaustion date by decades with a wide variety of relatively small policy changes. Yes, we should take both programs’ future solvency seriously, but lumping them together risks overreacting and undermining Social Security.