Probably one but you can't generalise.
Three. One to do it, one to complain that it has already been done before, and one to repost this joke.
100, 1 to screw it in and 99 to say how they could do it better.
How many did it take last year
How many pessimists does it take to change a light bulb? None - it's probably screwed it too tight anyhow!
