had researched some statistics a while back, like in 2004, may be useful as an older point of reference..

… the dropout rate from active youth group attenders to college is somewhere in the range of 67% to 78%, regardless of ethnicity.

Asian American anecdotal stories is still that 1996 Christianity Today article, “Silent Exodus,” citing about 80% for Asian Americans..

And, from http://www.barna.org/FlexPage.aspx?Page=BarnaUpdate&BarnaUpdateID=149 (a whole Barna report on 20somethings)::

Perhaps the most striking reality of twentysomething’s faith is their relative absence from Christian churches. Only 3 out of 10 twentysomethings (31%) attend church in a typical week, compared to 4 out of 10 of those in their 30s (42%) and nearly half of all adults age 40 and older (49%).

The low level of twentysomething church attendance is not just due to the “college years,” when many young adults may not have easy access to a church. The research shows that church attendance bottoms out during the late 20s when the vast majority of students have transitioned from education to the workforce. Just 22% of those ages 25 to 29 attended church in the last week.

Many twentysomethings are reversing course after having been active church attenders during their teenage years. As teenagers, more than half attended church each week and more than 4 out of 5 (81%) had ever gone to a Christian church. That means that from high school graduation to age 25 there is a 42% drop in weekly church attendance and a 58% decline from age 18 to age 29. That represents about 8,000,000 twentysomethings alive today who were active church-goers as teenagers but who will no longer be active in a church by their 30th birthday.

from http://youthworkers.net/PDF/NM21-1_1.pdf – Barna is quoted as follows:

Making the transition into college is tough. According to a 2000 report (“Third Millennium Teens”) by the Barna Research Group, “more than seven out of ten teens are engaged in some church-related effort in a typical week. When asked to estimate the likelihood that they will continue to participate in church life once they are living on their own, levels dip precipitously, to only about one out of every three teens. Placed in context, that stands as the lowest level of expected participation among teens recorded by Barna Research in more than a decade.” 

and from http://www.nehemiahinstitute.com/articles/index.php?action=show&id=20

One study of over 3,500 incoming freshman at various state and private universities who identified themselves as ‘born again’ Christians found that by their senior year, between one-third and one-half said they no longer considered themselves as such. 

1 implication is that church youth group are largely ineffective, and thus some hesitancy in youth pastors publishing these alarming stats.. others excuse the decline as a “phase” of individuation that people go thru, and allegedly some return to church after marriage and first child is born..

p.136 from Real Teens by George Barna (2001) 

One unmistakable indication of the brewing trouble comes from the response to a question concerning how likely teens say they are to attend church once they are independent. After they graduate from high school or move away from home, just two out of five teens content it is “very likely” that they will attend a Christian church on a regular basis, and another two out of five say it is “somewhat likely.” What makes these figures most alarming is that questions of this type typically produce an overestimate of future behavior. If we apply a “correction factor” to these responses, we would estimate that about one out of three teenagers is likely to actually attend a Christian church after they leave home. 

==== “Youth groups are attended by about one-third of America’s teenagers.” (p.112)