When it comes to estimating the size of demographic groups, Americans rarely get it right. In two recent YouGov polls, we asked respondents to guess the percentage (ranging from 0% to 100%) of American adults who are members of 43 different groups, including racial and religious groups, as well as other less frequently studied groups, such as pet owners and those who are left-handed.
they wouldn't be asking if it wasn't a big, big number
They could ask "What percentage of people live in Michigan" and I suspect they'd still get 30%