I cannot provide stats, but I can provide examples.
The congregation that I grew up in had two families that were the main pillars. The Presiding Overseer's (COBE) family and the Secretary's Family. Both brothers' wives are/were regular pioneers. Their kids (whom I grew up with) pioneered right out of high school and married Ministerial Servants.
Where I have seen the change is the grandchildren. I moved away when the grandchildren were still school age. Now they are grown and out of their parents' house. They are all inactive. They are all in relationships with non-Witnesses. They are tatted out and have pierced faces.
I really think that Generation X was the last generation the organization could count on. Generation X is cooling off and slowing down (i.e. just going through the motions). As the organization doubles down on stupid, Generation Y is woke to their propaganda.