Supriya Syal and Dan Ariely in Scientific American:
Only about half of the people who could vote in the 2012 U.S. presidential election actually did so (53.6 percent of the voting-age population). This puts turnout in the U.S. among the worst in developed countries. By way of contrast, 87.2 percent of Belgians, 80.5 percent of Australians and 73.1 percent of Finns voted in their last elections. In a nation quick to defend democracy both within its borders and beyond, why are more Americans not exercising what is arguably their biggest democratic right?
Certainly there are political and mechanical obstacles within the American voting climate that make it difficult for people to even get to the polls, such as onerous voter ID laws or a shortage of polling stations in some locales. The absence of automatic voter registration (as in Finland) or mandatory registration (as in Australia) also limits turnout.
But beyond these structural hurdles, most theories that examine the mindset of those who do not vote speak to disengagement from electoral politics or disbelief in government's ability to affect progress. Solutions that aim to address these problems typically inform people about the importance of their vote in electing a government that works for them. Yet this tactic does not appear to sway many. Despite such efforts, turnout has consistently hovered around 50 percent for the past nine U.S. presidential elections—the highest being 56.9 percent in 2008.
More here.