Budget deficits – when governments spend more than they raise – are growing around the world. In theory, countries can keep their deficits in check by lowering public spending or increasing tax revenues. Both, though, are usually unpopular with voters.

This can get complicated – just look at France right now. The country’s budget deficit was worth 5.8% of its economy last year, well above the eurozone’s 3% limit. And while a strong economy can lead to increased tax revenues, the French one is only plodding along.

That leaves the other option: spending cuts. Famously an unfavourable option, the French prime minister has called a confidence vote for Monday in a bid to secure support for the trims. If he doesn’t get enough votes – which seems likely – then he’ll be forced to resign.

Wary of all the “unknowns”, investors have sent long-term French government borrowing costs to their highest level in over 16 years. That’s a problem: higher costs force the government to either borrow more money or cut other costs. That leads to slower growth and lower tax revenues… meaning an even bigger deficit.

This isn’t an isolated incident. Many countries – including the UK, the US, and Japan – seem to have unsustainable public debt. So, wary of so-called “debt spirals” all around the world, investors have pushed up many countries' long-term bond yields.