The US government is tightening the reins on the number of employees and contractors with access to classified information. A report to Congress from the Office of the Director of National Intelligence said the number of cleared people dropped by 635,000 in 2014 from the year prior.

Despite the purge, that left a whopping 4.5 million people with security clearances. There was a nearly 15 percent reduction in new and renewed clearances, the report said. And government workers and contractors having "top secret" clearance declined by more than 100,000 people, to about 1.4 million.

"These decreases were the result of efforts across the USG to review and validate whether an employee or contractor still requires access to classified information and several additional Department of Defense (DoD) initiatives to review its cleared population," the April report said.

Secrecy News, published by the Federation of American Scientists, noted that it was the first reduction "in the total security-cleared population since the government began systematically collecting statistics on security clearances in 2010."

The implication is that the national security bureaucracy, including the national security classification system, is susceptible to deliberate regulation and is not, as sometimes appears, an autonomous entity driven obscurely by its own internal dynamic. It follows that additional changes in the size and structure of the national security system may be achievable.

The report noted that there was a 3.1 percent reduction in the number of individuals eligible for access as part of several government-wide initiatives "to review and validate the need of their personnel for continued eligibility for access to classified information."

The 2014 Report on Security Clearance Determinations, citing "multiple issues," said that hundreds of people waited for more than a year to get cleared. The most common single reason for delay was "foreign influence" followed by "financial considerations," the report found.

The government, the report concluded, "continues to face timeliness 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 National Security Agency reported the highest denial rate, at 9.2 percent. The lowest reported denial rate came from the Federal Bureau of Investigation, at 0.1 percent.