The global ratings agency Fitch this week lowered its assessment of the creditworthiness of the U.S. government, announcing that it had downgraded U.S. Treasury securities from the agency’s top AAA rating to a slightly lower AA+ designation.

In the long term, the change could have potentially serious consequences for the United States and the broader global economy. This is because debt issued by the U.S. Treasury is a global benchmark for interest rates and has long been considered one of the safest — if not the safest — interest-bearing investment in the world.