I'm surprised it's even 50%, it seems like it would be lower than that so I'm curious how how they defined it. Barna's 40% seems a bit more realistic though, so I am curious about how these questions were worded. I did look for specifics on masturbation and couldn't find any.
There are differences depending upon how you define Christian and in the question. Barna's article gives several different combinations. The lowest number is 40%. I would probably cite 41%, for the following:
* Question: is cohabitation a good idea?
* Definition: Practicing Christian: Those who attend a religious service at least once a month, who say their faith is very important in their lives and self-identify as a Christian
But this is across age groups. It varies strongly by age group (though their numbers by age group seem to be for everyone, not just Christian).
It also varies by question. They also give the answer to have previously or are currently cohabiting. For practicing Christians that's 48%. Since 41% say it's a good idea, some people are admitting that they've done things that aren't a good idea. Not a surprise. Most of us have done things we know we shouldn't have.
While they don't report numbers for practicing Christian by age, the difference across age is so strong that I think it's clear that more than 50% of practicing Christian millennials believe cohabiting is OK.
Since almost all churches disagree with this, it will be interesting to see whether official teachings change over time. The Catholic Church shows us (with homosexuality, and even more radically with birth control) that it's perfectly possible for a church to teach things that virtually all of their members reject. That seems less common with Protestants though.
There has been a fair amount of work among Biblical scholars and theologians to justify homosexuality. I'm not aware of much justifying sex outside marriage (though my church is an exception). What happens to a church where members reject teachings with no particular justification? If they do it here, do they still maintain the rest of the teachings?