It’s a basic fact of American politics:
It so happens that the gap between voters and non-voters breaks down strongly along class lines. In the 2012 election, 80.2 percent of those making more than $150,000 voted, while only 46.9 percent of those making less than $10,000 voted. This “class bias,” is so strong that in the three elections (2008, 2010 and 2012) I examined, there was only one instance of a poorer income bracket turning out at a higher rate than the bracket above them. (In the 2012 election, those making less than $10,000 were slightly more likely to vote than those making between $10,000 and $14,999.) On average, each bracket turned out to vote at a rate 3.7 percentage points higher than the bracket below it.
This class bias is a persistent feature of American voting: A study of 40 years of state-level data finds no instance in which there was not a class bias in the electorate favoring the rich—in other words, no instance in which poorer people in general turned out in higher rates than the rich. That being said, class bias has increased since 1988, just as wide gaps have opened up between the opinions of non-voters and those of voters.