I have no idea. As is traditional, I grabbed a statistic off Wiki.
The traditional approach by federal prosecutors, I believe, is to greatly overcharge and then grudgingly agree to a more reasonable plea bargain, accepted by the accused who is still in shock from the initial charges.
Pushing something to mid trial and backing out at that point wouldn’t count, I’d think. I.e. if the prosecution can actually see that it is in trouble. It’s trials that reach verdicts that would count.
I think it is the Institute for Justice and others that are bringing up the evils of prosecutors leveling extra and extraneous charges to force people to plea bargain, so that those who don’t plea bargain face two and three times as much time in jail if they lose, and they usually lose.