I won't attempt to guess a percentage. I DO know that my "first" Confirmation was invalid due to defect of form and matter. The other five dozen or so with me were also not Confirmed. I know the baptisms of both my nephews, in 1998 and 2007 are invalid. The form was wrong in both, and matter in the second.
The Confirmandi high schoolers wrote "a creative liturgy" which the Bishop used in 1974. There was no oil used, but I recall processing outside in a conga line to the beat of bongo drums and a sitar. There was a group photo with the bishop, then everyone went home. Decades later, I requested a record of this and all that was found was a yellowed sheet of loose-leaf paper with penciled names some checked, some crossed off, some with question marks. This was stuck in the back of a large binder from the parish which has since gone out of existence. The binder was in the basement of neighboring parish. There is no record with the diocesan headquarters.
At both baptisms, the words, "You are initiated a child of the Father, the Creator, the Spirit. Welcome to the family of God," were substituted. At the 2007 baptism, a "eucharistic minister" sprinkled holy (?) water while the priest (?) said the incorrect words from his wheelchair. He had broken both arms and legs in an auto accident, and was therefore literally unable to baptise anyone.
It's just as well on the baptisms because the children haven't entered a house of worship since. They were raised "not-religious." They were baptized to appease an elderly relative whose house they were living in, free of charge.