This is anecdotal of course, but my observation of born-in JWs is about a 1/3 retention rate. I grew up in a fairly large western U.S. city with a lot congregations. Within my generation X in that city, at least 3/4 are faded or df'd. Most have easily maintained relationships with still in family. Most of the congs in that city only had about 50% of their publishers living in their territory boundaries--so many people just attended where they wanted (even elders). So fading was pretty easily done and keeping track of of who was actually "in" was pretty loose.
Conversely, my husband grew up in a small Midwest town surrounded by rural farmland. Only one congregation within a radius of one hour drive. Very little movement in the area. Entire congregation are born ins. 3-4 generations in each family in the same congregation, so less people leave. Most are related to each other by blood or marriage, so the congregation and their family are kind of one in the same. And those who get df'd seem to return for reinstatement, probably because they are more anchored to the religion. Also, everybody knows everybody's business, so there isn't really the option of discreetly associating with faded or df'd family. Who knows how many are mentally out though.
Now we are in a different area than either of us grew up in, but it's a lot closer in JW practice to the area my husband grew up in. I have to say it has been both suffocating and eye-opening. I think it hastened my awakening to the TTATT. Growing up in a looser, more liberal JW world kept me loyal and believing WT was a reasonable religion.
Also, anecdotally, Generation X born in men in my area are not "reaching out". Positions are mostly held by baby boomers and old timers, with a few uber young men who still live at home. The family men keep responsibilities in cong minimal to none.