The fact that economics tell us to discount — as in make less of — each dollar owed or received in the distant future, however, doesn’t mean a government can ignore those obligations and receipts, especially if there are loads of future obligations relative to receipts.
Take the just-released 2013 Trustees Report on Social Security’s long-run finances. Table IVB6 shows an infinite horizon fiscal gap of $23.1 trillion separating the Social Security system’s projected costs and taxes after taking into account the several trillion in the Social Security trust fund. To give you a sense of how massive this shortfall is — and it grew by fully 8 percent last year alone — it is 50 percent larger than U.S. GDP and almost twice the size of total federal debt held by the public.
Table IVB6 also reports Social Security’s fiscal gap over the next 75 years. It’s much smaller — only $9.6 trillion, and that’s the number people tend to use in discussion. But that number is only 41 percent of the actual economic gap: $23.1 trillion. Thus, the 75-year fiscal gap hides three fifths of the system’s true long-term shortfall.