From the fine fellows over at The Monkey Cage (a blog run by political scientists who don't swear nearly as much as I do, which may be why they all have jobs):
A casual visual inspection suggests that people in their forties are more Republican than any other age group. Unfortunately that is one of two potential interpretations, the relative merits of which cannot be determined by this data. Are people aged 40 to 50 more conservative, or are the people aged 40 to 50 right now more conservative? This is a very old debate in the social sciences, the endless squabble over life-course effects versus age-cohort effects.
We could easily construct a story that supports either argument. For example, it's logical to suggest that people between 40 and 50 are bound to be a little less liberal, having settled into a life of property taxes, car payments, and saving for college. Conversely we could argue that the individuals between 40 and 50 today are more conservative because of the 1970s. They became politically aware during a thoroughly depressing era and experienced Carter Malaise followed immediately by Morning in America.
Short of doing decades-long panel data studies (and those have plenty of critics too) it's virtually impossible from a social science perspective to distinguish between these possibilities. I'm simplifying things, for certainly many researchers have devised innovative ways to support one argument or the other. But it is fair to say, as someone with no horse in the methodological race, that it remains an open issue.
On a personal note, I have long considered the first possibility – that aging makes us Republicans – to be overwhelmingly depressing. Ginandtacos nation, this post serves as binding legal authority for one of you to smother me with a pillow if I ever take up Tax Bitching as a hobby or cheerlead pre-emptive wars in the hopes of getting some great new footage for Wings.**
**The one on the Military Channel, not the delightfully crappy 1990s sitcom. I know there are only so many times one can watch the same episodes ("Wings of the Luftwaffe") but there is a moral limit to what I am willing to support to acquire new footage.