From the book...
The late J. Allen Hynek, Air Force astronomy consultant for Project Blue Book and founder of the Center for UFO Studies that now bears his name, once referred to the sheer number of UFO reports as an ‘embarrassment of riches.’ The numbers would certainly seem to bear him out. One Gallup public opinion poll revealed that nine percent of the adult American population, equivalent to about 11 million people at the time, had seen what they thought was a UFO. Extrapolated worldwide and over time, the number of UFO witnesses from the last half century alone easily extends to the tens, if not hundreds, of millions–only a minuscule fraction of which are ever reported to the military, law enforcement officials, or civilian UFO research organizations.
This inherent embarrassment of numbers includes an embarrassment of forms as well. Obviously, if we had had, say, 37 million reports of the same object since Kenneth Arnold's landmark 1947 sighting, we would all be more or less agreed that an invasion of advanced and presumably extraterrestrial technology was now well under way. But the fact of the matter is that UFOs are routinely reported in a vastly bewildering variety of shapes, forms, and behavior. It's one thing to contemplate that we're being visited on a regular, if not daily basis, by extraterrestrial visitors. But it's quite another to posit the position that planet Earth represents little more than a convenient truck stop on some intergalactic highway, a brief stopover between one edge of the Milky Way and the other for every passing vehicle of alien manufacture and its occupants.