Hunderds of thousands if not millions by now. My dad was carreer Air Force, and I grew up ten miles from a commercial airport.
They tend to be narrow near the jet and wider further back as the moisture dissipates and spreads outwards.
Almost always, but they are never wider, more spread out, thicker and more dense the further away they get. Those that dissipate become less integral, more translucent and less dense, as is the sublimative dispersal nature of that which dissipates.
Indeed, that is what helped to convince me of the fact that this was a missile launch; the thicker part is also more dense, gelatinous and opaque, as would be a launch exhaust. Also, a jet contrail would not curve all the way to the ground except shortly after takeoff; on a flight asserted to be coming from across the Pacific, the wider, less-dense dissipating tail would trail off into the same upper strata in which the jet flew.
I know it's not normal, nor should it be expected that you would assume that you're conversing with somebody who has a 160-plus I.Q., and that it is far more de rigeur to be speaking with someone who is less than totally observant and who does not possess a true photographic memory.
Perhaps that contributed to your assmptions concerning what you mistook for my more commonplace powers of observation and ratiocinational deduction. Not to worry, I understand. I mean, I really understand.
;-|
That is one aspect that the missile-deniers are ignoring. The contrail is thick and opaque its entire length. Also, while it is true that a jet contrail often continues to widen to a point as it ages (until it dissipates into nearly invisible haze) it will appear to get narrower towards the horizon as it is many miles further away.