During periods of high and growing federal government debt levels in the early 1990s and following the global financial crisis of 2007–2008 (the Great Financial Crisis), economists and policymakers acknowledged the costs and looming dangers of an unsustainable fiscal trajectory.1 In light of these concerns, policymakers reduced public expenditure (as a share of GDP) in the 1990s to sustainable levels and commissions were established in 2010 in an attempt to achieve fiscal sustainability in the long run.2 Following the 2020 COVID-19 recession, the debt-toGDP ratio of the United States now exceeds the size of the economy for the first time since World War II. What is most intriguing about this dangerous fiscal milestone is that this time around, broad acknowledgment of the unsustainability of our fiscal trajectory is largely absent. Instead, several economists have propounded new definitions of fiscal sustainability that place greater emphasis on real interest rates and the interest rate–minus– growth differential (r − g)