It's practically impossible to know the exact figures, theres over 13k cmdrs involved..
.. but if i'd have to guess, i would say:
- 25% didnt even start the journey for a reason or another. (that happens, people love to register to stuff without even real intention of actually participating, other reasons being real life stuff, forgetting that you registered to some expedition over a year ago, etc etc.)
- 10% who actually started dropped out soon after the start because they got ganked and they didnt join PG for a reason or another (over 1000 cmdrs got killed at Pallaeni already, according to certain individuals)
- 10% dropped after the first CG
But, because for example console players EDSM inputs is a bit more difficult, i say theres approx 20-30% of cmdrs who are active but doesnt show up in there.
So, my estimate is that there's approx 65-75% of the initial roster left and EDSM backs up my estimates.
EDSM roster involves approx 50% of the whole roster and not more than 31% (plus those 10-15%who cant update their progress) has reached WP4.
Rough estimates but i dont think the real figures are that far off..