A new report to Congress from the Office of the Director of National Intelligence (ODNI) gives precise and somewhat startlingly large numbers of persons with security clearances.
The report (made available by FAS) numbers are a little hard to add up because it conflates government employees and contractors (something of a sign of the times) but are listed as follows:
(A) Number of government employees who -- (i) held a security clearance at such level as of October 1, 2010; • Confidential/Secret: 2,166,679 • Top Secret (collateral and TS/SCI): 666,008 (ii) were approved for a security clearance at such level during the preceding fiscal year. • Confidential/Secret: 512,076* • Top Secret (collateral and TS/SCI): 130,755* (B) Number of contractors who -- (i) held a security clearance at such level as of October 1, 2010; • Confidential/Secret: 541 ,097 • Top Secret (collateral and TS/SCI): 524,990 (ii) were approved for a security clearance at such level during the preceding fiscal year. • Confidential/Secret: 512,076* • Top Secret (collateral and TS/SCI): 130,755*
(Numbers with an asterisk mix government employees and contractors.) Steven Aftergood of FAS derives the number of people with security clearances as 4.2 million.
Just last year in the WaPo series Top Secret America Dana Priest and her colleagues claimed there were over 854,000 Top Secret clearances–an amazing number by itself that this report actually exceeds. This report suggests that 1.3 million people actually hold TS clearances.

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