At least, if you’re a Protestant:
Note that 0 means either a round-down or a not measured that year.
Protestants can take partial comfort in the thought that Christian (non-specific) may contain sympathizers, but in the end it's a little hard to get around the notion that the Protestants have fallen a long ways from their dominance of the late 1940s.
I think we're seeing a graphic demonstration of two kinds of people here: those who insist on seeing miracles and God in everything, and then everyone else, who often discovered praying doesn't get you anything but some physical rest. Or was that in poor taste?
Otherwise noteworthy? The well-publicized rising of the Nones, from virtually nothing to 20%. The exact content of this group is a little more confusing than others, though - it's not a mob of eye bulging atheists, if that's your worry. It's more of a catch-all for those who don't fit in anywhere else; I'm sure there are many "spiritual" types, which is a category I've never understood.
What does it all mean? Well, the evangelists, who are mostly Protestants as I understand it, are getting a little frantic, as does any group that finds itself transitioning down the social ladder, especially when it's from being #1. Not that they're off the top of the ladder just yet, but they can see the cessation of their dominance from where they dangle.
And thus the apocalyptic cries to which we're subjected these days.
Otherwise, it's really a sort of empty graph. Finding knowledge in it is a bit of a quest.