Fans of Portugal react as they watch the Euro 2016 soccer match between Portugal and Poland at a public screening in downtown Lisbon, Portugal, June 30, 2016. Rafael Marchante/Reuters Debt is a function and a fixture of any working economy. Governments borrow to fund spending on things like roads, hospitals, and schools, as well as to fund promises like tax cuts.

Debt-to-GDP ratios around the world have increased in recent years as governments take advantage of historically low interest rates to pile up cheap debt before rates inevitably begin to rise.

Borrowing is a good thing for a working economy, but unchecked borrowing can be a bad thing, especially in an economic downturn. Even cheap debt can become unaffordable if a country has too much of it and output begins to slow.

The level of gross government debt as a percentage of GDP can indicate how able a country is to pay back debts without incurring further debt. Basically the lower the debt-to-GDP ratio the better.

The CIA's annual World Factbook, a huge and pretty comprehensive compilation of data and statistics from all over the world, includes figures on nations' debt-to-GDP ratios from around the world.

Numbers are given as a percentage of GDP, so if a country has a GDP of £100 billion and a gross debt of £110 billion, it has a debt-to-GDP ratio of 110%. Here are the 23 nations with the highest debt-to-GDP ratio: