The upcoming election raises the important question of whether it's rational for you to vote. You might think that the answer is obviously "yes." But economists and other rational choice theorists have long argued that voting is irrational. Why? Because there is only an infinitesmally small chance that your vote will make a difference. In a U.S. presidential election, the chance that one vote will decide the outcome is less than 1 in 100 million, and it is still extremely small even in elections for the House or Senate. Thus, the 30 or 40 minutes of time that it takes to vote is probably far more valuable than whatever benefit you hope to derive from the "right" candidate winning, if the latter is divided by the ludicrously tiny chance that your vote will be decisive.
Critics of rational choice theory, of course, have had a field day arguing that rational explanations of human behavior are invalidated by the obvious fact that millions of people do vote, despite its being irrational to do so. The critics are, quite rightly, not swayed by arguments that voting is rational because people feel they have a "duty" to go to the polls. After all, why would it be rational believe you have a duty to do something that makes no difference? Duty-based explanations don't rescue rational choice theories of voting; they just add another layer of irrationality to the mix.
In fact, however, both sides are wrong. It is indeed rational for many people to vote, and therefore the existence of widespread voting is not evidence against the validity of economics or rational choice theory. For a detailed explanation, complete with equations, see my forthcoming article here.The key insight is that the traditional rational choice theory of voting implicitly assumes that the voter cares only about their own self-interest, narrowly defined. But if you care even slightly about the potential benefits to fellow citizens of ensuring that the "right" candidate wins, then the sum total of those benefits might well outweigh the (generally low) costs of voting even after discounting for the fact that there is only a minute chance that your vote will make a difference. Real-world voters, of course, probably don't go through detailed calculations of the sort that I describe in the article. But they do likely realize that their is little chance that their vote will make a decisive difference, while also caring at least slightly about the welfare of their fellow citizens. And the combination of these two assumptions is enough, for many people, to make a rational decision to vote.
Of course, under these assumptions, it will be rational to vote only if you perceive a significant difference between the two opposing candidates or parties. And, as I note in the paper, studies do indeed show that those who perceive a big difference between the two sides are far more likely to vote than those who don't.
This theory is not entirely original to me; it was in fact proposed by philosopher Derek Parfit in his 1984 book Reasons and Persons (pp. 73-75); what I have done is explore its implications for voting theory more generally. Until now, Parfit's theory has been largely ignored by academic scholars of voting, perhaps because Parfit is not an economist or political scientist, and his book is primarily devoted to other subjects.
Not all the implications of the Parfit model are reassuring. As I show in my article, despite the fact that it is rational to vote, it is also rational for most people to be poorly informed about politics (primarily because acquiring and processing political information is much more costly and time-consuming than voting). For the minority that is well-informed, it may well be rational to analyze the information they do have in a biased and illogical way. Thus, a rational population is likely to have a large number of people who choose to vote but also tend to be ignorant and/or illogical about politics.
UPDATE: Some commenters argue that it's rational to vote because of the chance that, even if your vote isn't decisive, it can send a "message" about the degree of support for a particular candidate, policy, or party. But the same logic applies here. The chance that the "message" will be "received" is only infinitesmally greater if Candidate X gets 10 million votes than if he gets 9,999,999. The impact of any one vote on the probability of successfully sending a message is unlikely to be much greater than its impact on the probability of winning the election.