Fitch just downgraded the U.S. credit rating — how much does it matter?

Fitch downgraded the U.S sovereign rating. The markets took the decision largely on their stride — but that doesn't make the decision inconsequential. (Samuel Corum/AFP via Getty Images)

In the financial world, it's akin to the gold standard: AAA, three letters meant to denote the safest possible investment.

The U.S. had proudly held to that top-notch debt rating for decades, reflecting its status as the world's biggest — and safest — economy, one that has never defaulted on its debt obligations.