"This goes back to 1982, when the Reagan administration began a program of such aggressive classification that the unofficial slogan was, "When in doubt, classify." This waned under Bill Clinton but shot back up dramatically under George W. Bush, so much so that by 2004 the mere bureaucracy for classifying documents cost $7 billion per year."
https://www.vox.com/2016/1/29/10873106/hillary-clinton-email-top-secret