From Wonkblog, using data from the Pew Research Center.
A full two-thirds said they simply didn't have enough time to vote. More than half of this group - 35 percent of the total - said that scheduling conflicts with work or school kept them from getting to the polls last Tuesday. Another 34 percent of the total said they were simply too busy, or that they were sick, out of town, or forgot about election day.
Twenty percent said they didn't like the candidates, didn't know enough to vote, or simply didn't care. And another 10 percent said that technical difficulties kept them from the polls - a missed registration deadline, a recent move or lack of transportation.
In short, voters didn't make it to the polls for two overarching reasons - either they were indifferent and couldn't be bothered, or there were structural forces conspiring against them - rigid job/school schedules or difficulties with the voting process overall.
