The number of people who held security clearances for access to classified information increased last year to a new reported high of more than 4.8 million persons as of October 1, 2011, a new intelligence community report to Congress said.

Last year’s annual report, the first official count of security cleared personnel, had indicated that there were over 4.2 million clearances in 2010. That number astonished observers because it surpassed previous estimates by more than a million. (“Number of Security Clearances Soars,” Secrecy News, September 20, 2011).

But it turns out that the 2010 number itself underreported the number of clearances, and the new report to Congress presents a revised 2010 figure of 4.7 million. Even so, the number of clearances rose in 2011 by about 3% to 4.86 million, the new report said. [Clarification added: Last year’s report used a methodology that tallied access to classified information. The resulting figures are not directly comparable to the figures presented this year. The new report focuses on eligibility for access, which yields a higher number of clearances both for last year and this year.]

The total clearance figure is composed of cleared government employees and contractors, at all clearance levels — Confidential, Secret and Top Secret. (The number of Top Secret clearances alone was over 1.4 million.) It includes all persons who have been cleared for access to classified information whether or not they have actually been granted such access. While the total reported figures are “likely to include some duplicate entries,” the report explains, efforts have been made to eliminate them and only “a minimal number of duplicates” remain.

The annual report on security clearances was required by Congress in the FY2010 Intelligence Authorization Act. It represents a new degree of transparency in national security classification policy. Until the first report was issued last year, only rough estimates of the size of the cleared population were available, and those estimates proved to be unreliable.

The latest ten-page report includes numerous details that are ordinarily withheld from public disclosure, whether they are classified or not. For example, the new report indicates that 5.3% of the security clearance cases that CIA processed last year resulted in denial of clearance. At NSA, the number of denials reached 8.0%.

Six of the seven intelligence community agencies that do their own clearance adjudications reported that they had cases that had been open for more than one year, the report said. The number of pending security clearance cases at CIA requiring more than one year to complete was 3,755 for government employees, and 732 for contractors.

“The IC faces unique challenges in clearing individuals with unique or critical skills — such as highly desirable language abilities — who often have significant foreign associations that may take additional time to investigate and adjudicate,” the report said.

The new report was transmitted to Congress in early July, and was first mentioned in a July 12 report from the Government Accountability Office. The report itself was publicly released last week by ODNI in response to a request from Secrecy News.