I think it's based on 4 different scenarios over the next 30 years: 1. Raise taxes by 20% w/o slowing the economy 2. Cut discretionary spending by 50% 3. Real economic growth of 8-10% 4. Print money to induce sustained 8-10% inflation The model thinks that only the option 4 is possible which creates an annual interest payment of $5T over the next 30 yrs. It's a River research by Sam Baker.