$4 trillion? Try $106 trillion, the medium estimate. That’s $106,954,000,000,000. Even the lowest, extremely conservative estimate comes in at $72 trillion; the highest is over $120 trillion.
The amounts are so large that some controversial reforms appear inconsequential in comparison. Take Obama’s “chained CPI” proposal: it would save an estimated $89 billion over ten years, or 1.3 percent of the total deficit over those same ten years.