Well, if you look at
the study that’s at the bottom of the trend piece, it doesn’t really say anything about premarital abstinence.
What they’re looking at, I think, is whether as a young adult people were more likely to be sexually inactive as someone who is now age 20-24, or as someone born in the 60s. What they find is that 6% of people from the 60s were sexually inactive after age 18 when they were in the 20-24 age group vs. 15% of those people today.
That’s a big jump. But also remember that marriage rates are way down and the age of marriage is up. So if you segment the population into people who wait until marriage and people who don’t, in the early generation a much larger proportion of the wait-til-marriage group would have been married when they were 20-24. While we can see that the sexually active/inactive split has shifted towards the inactive group we don’t know how the wait/don’t wait split has shifted.
That’s not to say that abstinence before marriage isn’t rising, but the study doesn’t address that question.