Also notice that Social Security — far from adding to the deficit or debt — is America’s largest creditor. Failure to grasp this distinction is like not understanding the difference between your home loan and the bank to whom you owe the money.
For the last few decades, Social Security has generated a surplus every year (in anticipation of the Baby Boomers retiring), so the trustees invest the surplus in U.S. Treasuries that generate interest of about $100 Billion per year, which gets credited back to the Social Security Trust Fund. That makes more fiscal sense than sticking the surplus in the sock drawer (i.e. lock box) where it would earn nothing and get eaten up by inflation.