Debt-to-GDP ratios do not predict fiscal outcomes. As ratios of government debt rise, some societies manage to deliver more responsible fiscal behaviour. Low debt ratios often mask dangerous currency or maturity mismatches which can suddenly impair banks and governments. Contingent liabilities, especially arising from the banking system, have the power to undermine sovereign creditworthiness. The demand for government bonds can behave unpredictably, and governments can suddenly find themselves cut off from financing. Official institutions like the IMF, European Commission, and World Bank have done themselves and their member states a great disfavour by obsessing about debt ratios which do not have clear implications for debt sustainability.