Children who become Christian

For an article, I'm working on tracking down this "71% Christians got saved young" figure to understand it better. Looking for the original source.Wikipedia post on Child evangelism movement pointed me to: "The Great Commission to reach a new generation," Thom Rainer, 1997, SBTS "Evangelism is most effective among kids," Barna, 2004 "The Bridger Generation," Thom S. Rainer, 2006 Also been referred to research by OneHope. An initial review shows this to be interesting. My own speculation is that most Christians got saved young because they grew up in Christian households. I'm looking to see if the original research cited here distinguishes between converts who were in Christian homes vs converts who were in non-Christian homes. (45 million babies born to Christian homes vs 15 million converts in from non-Christian homes, globally, per year, according to Global Religious Dynamics.)