How can this percentage be so high?

80 per cent of Americans surveyed by the CNN TV news network believe that their government is hiding evidence of the existence of space aliens.

http://cosmicvariance.com/2005/10/02/the-world-eyes-american-ignorance/#comment-4413

I dont believe it simply because thatd mean nearly everyone I saw walking down the street was an alien-conspiracy-nutjob

But if theyre just 99% bureaucratic crap then whats the harm in keeping it secret? It isnt like anyone within the American public is going to care to read it. They already have regular declassifications, which should convince the public that theyre not hiding anything that important beyond new weapons systems and such - but the public still wants to believe in the crazy alien conspiracies