Americans are losing their religion at an unprecedented rate, with fully one-quarter of adults saying they belong to no church or religious institution, according to a new survey from the Public Religion Research Institute. These religiously unaffiliated adults are more numerous than members of any single church or religious group.

The findings dovetail with a Pew Research Center survey published earlier this year that found that the non-religious are now the largest religious voting bloc, outnumbering political heavyweights such as Catholics and white evangelical Protestants when it comes to registered-voter numbers.

But the PRRI survey explains why it seems highly unlikely that the unaffiliated will be a potent force at the ballot box this fall: Many of the religiously unaffiliated don’t bother to vote.