The U.S. intelligence community reports that more than 4.2 million people held security clearances last year. It's the first formal count of clearance holders and produced a much higher number than previously estimated.
The report to Congress was required by the 2010 Intelligence Authorization Act. The report says more than 666,000 government workers hold Top Secret clearances, as do more than 524,000 federal contractors. The rest have lower clearances.
One recent effort to find out the number of people with security clearances came up short. In 2009, the Government Accountability Office, the investigative arm of Congress, estimated that about 2.4 million people held clearances, excluding some of those with clearances who work in areas of national intelligence.