The article develops a way to figure out the maximum amount of debt a country can handle. It depends on factors like how much money the country expects to make, how fast it's growing, and how much debt it plans to take on in the future. The researchers came up with a simple formula to calculate this maximum debt. They also found a way to estimate the chance of a country defaulting on its debt based on how much debt it has compared to its income. After testing this on 23 countries, they found a strong link between the interest rates countries pay on their debt and the likelihood of default.