MsJack wrote: And what % within that subset are active, practicing Christians?
It's really tough to get a good number on a question like that. First, because people identify with a religion culturally and will report being a Christian in the same way I say I'm German even though I've never been to Germany. Second, people tend to drastically over-report their religiosity on open survey questions because they view it as a report of being of good character. Church attendance rates are, for example, overstated by an order of magnitude when people are asked about it compared to censuses of Church activity. Asking people if they are an active, practicing Christian is like asking them if they are faithful to their spouse.
So, it'd be hard to find numbers on his that aren't going to overstate what your anecdotal experience would suggest.