The map uses the prices of credit default swaps, which are derivatives that pay out if a borrower defaults.
Sovereign credit default swaps have been used as a type of insurance against sovereign governments not paying back the money they owe. Like any insurance product, the more expensive it is the more likely the event you’re insuring against will happen soon.
Venezuelan debt is by far the most risky, costing twice as much as Greek or Ukrainian debt to insure.
The graphic also shows just how far Spain and Ireland have come. The market thinks their debt is pretty risk free, with lower CDS spreads than Italy or Portugal. The Spanish economy is going through a bit of a revival after suffering a devastating housing crash and unemployment crisis.