There is no formula or numbers, having read many, many posts on here and some other books it is always about getting yourself back first and foremost - if you are not back they will never come back, working on why the relationship failed. Addressing any issues or learning you need and becoming the person you once were before the relationship (as we are all guilty of changing when with somone!)
Will they come back - who knows it depends on to many variables - Love, compatibility, if females then their intuition on how suitable you are for them, also their emotional thought process as women are guided by both these last points, Regret, Time and NC help the most I think - but life has only two certainty's....!
To tie it to the OP - I would guess maybe 20 - 30% come back within a short period (
Maybe 5 - 10% come back longer - 6 months or more - when both people have grown success is more likely