But then, from Yahoo Answers Questions I have seen, many US 'Protestants'. do not accept their lineage of Christianity as being traced thru The RC Church, posing such revealing questions as "Are Catholics really Christians?"
Thanks for that, Foolestroupe. I agree that many other Christian sects also accept the earth is much older than 6000 years. Whether a specific group of believers is included or not, though, would be a distraction. Many believers who take the Bible very seriously do not think that the New Testament asserts that Genesis should be taken literally. My suspicion is that it is many more than do take it literally, but the question arises how do you get any figures in support of that? (Looking for evidence, folks! The scientific approach strikes again!). The size of the RC church was something I had in the trivia-loaded part of my brain, and being hierarchical it is possible to make a statement about 'What the RC Church' beliefs are. Ditto Anglicanism.

Consulting Wiki, I see I was right about RC being largest. I was wrong about the position of Anglicanism, but it is still one of the largest groupings. I'd completely forgotten about the Orthodox churches, which are substantial, but a minute or twos search didn't reveal what age they think the Universe is, and I lost interest... Similarly Baptists are one of the largest groups, but as individual churches do not necessarily believe the same as their neighbouring churches it is impossible to make a reliable statement about what Baptists think the age of the earth is.

If anyone knows how go give a breakdown similar to Wiki on who believes what about the age of the earth, I'd be glad to see it.