On average, Americans thought that 32 percent of Democrats are gay, lesbian or bisexual. The correct answer is 6 percent. And they thought that 38 percent of Republicans made more than $250,000 a year. The correct answer is 2 percent.

It goes on from there. Americans overestimate the percentage of Democrats who are black, union members or atheists. They overestimate the percentage of Republicans who are seniors, evangelicals or Southerners.

These misperceptions are even worse when people are evaluating the opposite party. Democrats overestimate the fraction of Democrats who are union members by 25 points. Republicans overestimate it by 34 points. Republicans overestimate the fraction of Republicans who are wealthy by about 30 points. Democrats overestimate it by about 40 points.