If you still haven't decided whether or not to vote, I'm not sure whether the article "Vote for Charity's Sake" written by three economists in the Election 2008 edition of The Economist's Voice, will convince you, but as an insight into the wacky workings of the economist's brain it's pretty funny.
Aaron S. Edlin, Andrew Gelman and Noah Kaplan start off with a dilemma.
As the election approaches, please remember to be kind to any economist you know. Economists feel on election day a little like Jews feel on Christmas. Participating makes them feel like a traitor to their kind but boycotting the extravaganza makes them feel estranged from the rest of society....
An economist who votes commits an irrational act, and to an economist irrationality is a sin. Why bother spending half an hour or more going to the polls and waiting in line when the chance is infinitesimal that your vote will affect the outcome? Yet, what is the other choice? Not voting. But, an economist who doesn't vote must squirm when others ask that day: "Have you voted yet?" Any explanation about the irrationality of voting will be scorned.
Then, in classic economist fashion, they solve their problem by pulling an initial assumption out of what appears to be thin air:
The two candidates have significantly different policies, and it seems plausible that the average benefit to the citizenry is $1000 or more per citizen to have the better candidate win. If one candidate makes global depression, nuclear war, or global climate change less likely, the benefits might be much greater.
The authors then run the numbers using a couple of other assumptions, and conclude that for voters in a key battleground states like New Mexico, "voting on the better candidate is equivalent to giving roughly $50,000 to charity (i.e., to others.)"
I make no pretense to judge the argument. If you'd like to examine it in more detail, you can read the whole thing for yourself here after jumping through a couple of hoops to get guest access.
I just find the whole convoluted process silly. Voting is a privilege and a right given to us by virtue of living in a free society -- we don't need a rational choice framework to provide a reason for participating in the process. "Vote for Charity's Sake" reminds me of an argument Tyler Cowen made in his book "Discover Your Inner Economist" discussing the incentives for a man to put the toilet seat down in a habitation shared with women. Sometimes, it's enough just to be polite -- we don't need an incentive.