Notice that while the liberal line is on a consistent gentle upward slope over time, the conservative and moderate lines exhibit mirror-image chaos. There's a blip in mid-2006, but the extremists don't really hit their stride until the election of Barack Obama. See the ideological cleansing take hold as "moderate" becomes a dirty word. What other result would you expect then, four years into it, when you subsequently ask people to self-identify?

Do you notice that the slope of the curves is changing in the present day? The liberal line took a small hit in 2010 lagging behind the hit moderates took in 2009, then it recovered its steady upward slope. Moderation is currently flatlined, but see that decline from 51% to 46% on the hard-right line? That trend will continue, I guarantee it. Slowly but surely the country is regaining its senses.

The other thing I find significant about this graph is what it doesn't show. It starts in 2001, maybe just before 9/11, maybe not. That's a serious omission, because the trauma of 9/11 frightened a lot of Americans into that conservative state of mind characterized by fear, pessimism, and angry bluster. Did all those people have an epiphany about economic theory on 9/11? Or did they just get the shit scared out of them?

You may prefer to focus on comfortable abstractions like economic theory, Tom, but in the real world, for most people, conservatism is a state of mind.