Government debt is one of humanity’s great inventions. It allows societies to store wealth, fight crises and build for the future. After Britain’s superior access to credit helped it defeat Napoleon in 1815, one historian likened the country’s credit lines to Aladdin’s lamp. Two centuries later, during the covid-19 pandemic, much of the world looked on with similar astonishment as rich countries borrowed freely to splurge on support for households and health care.