In most countries, the government takes the lead in getting people’s names on the rolls – whether by registering them automatically once they become eligible (as in, for example, Sweden or Germany) or by aggressively seeking out and registering eligible voters (as in the U.K. and Australia). As a result, turnout looks pretty similar regardless of whether you’re looking at voting-age population or registered voters.
In the U.S., by contrast, registration is mainly an individual responsibility. And registered voters represent a much smaller share of potential voters in the U.S. than just about any other OECD country: Only about 65% of the U.S. voting-age population (and 71% of the voting-age citizenry) is registered, according to the Census Bureau, compared with 96% in Sweden and 93% in the U.K.
As a consequence, turnout comparisons based only on registered voters may not be very meaningful. For instance, U.S. turnout in 2012 was 84.3% of registered voters, a relatively lofty seventh among OECD countries. But registered voters here are a much more self-selected group, already more likely to vote because they took the trouble to register themselves.
Political reformers often overlook a major reason for apparently low US turnout. The United States has more elected offices (more than half a million) and elections than any other major democracy. We call on people to vote in primaries, special elections, and municipal elections, with election calendars that vary greatly from state to state. We vote on everything from community college trustee to president. Voter fatigue is a big part of the story.