The number is pretty hard to calculate because it should include any obligation, not just official debts. If the government promised to, say, cover certain expe

The number is pretty hard to calculate because it should include any obligation, not just official debts. If the government promised to, say, cover certain expenses in retirement like health care, the true debt should include a realistic estimate of just how much that health care would cost. Not that anyone can predict which new treatments will appear or what they would cost.