"The starting point for our calculation is work done by Alan Auerbach and William Gale, two economists who are experts on the federal budget. Mr. Auerbach and Mr. Gale have written two recent papers that review what they call “the dismal prospects for the federal budget.” As an extension of that work, they built a spreadsheet for The Times that analyzed the savings that the government would need to achieve each year starting in 2015 to keep the deficit at 3 percent of gross domestic product. That’s the level that many economists consider sustainable for the deficit, because one year’s normal economic growth can pay off the previous year’s budget shortfall."