SS represents an unfunded liability of close to $40 trillion. It is a pay as you go program where today's workers pay for today's retirees. It has been running in the red since 2010. In order to make up the shortfall and pay full benefits, the General Fund must redeem the non-market, interest bearing T-bills in the SS Trust Fund. Since 40% of the General Fund is from borrowed money, we are borrowing money to pay for SS.
Nice summary.