New U.S. citizens wave flags during a special Flag Day naturalization ceremony at the New-York Historical Society in New York in 2016. (AP)
Contributor, Monkey Cage

Here is a question: “Out of every 100 people living in the United States, how many do you think were born outside of the country?” It’s not a fact that most people have at their fingertips. And when people guess, both Americans and Europeans tend to overestimate the size of the immigrant population. In one study, Jack Citrin and I found that Americans thought that the foreign-born were 28 percent of the U.S. population. The actual figure at that point was 12 percent.

It’s natural to think that these overestimates must be consequential for how people think about immigration. People who overestimate the immigrant population might therefore think it constitutes a bigger threat and want to reduce it.

But in a new paper that is forthcoming in the Journal of Politics, Dan Hopkins, Citrin and I show that this may not be true: Correcting misperceptions about the size of the immigrant population didn’t consistently affect attitudes about immigration.

Our study is based on seven separate experiments that we conducted over the past 11 years. In each case, a nationally representative sample was randomly split into different groups, some of whom saw correct information about the size of the immigrant population. The typical way we did this was via a simple statement like:

“We are interested in whether you’ve heard about a story that has been in the news. The story is: the Census Bureau has estimated that about 12 out of every 100 people living in the United States are immigrants who were born outside of the U.S. Have you heard about this story?”

Some respondents saw this information and then were asked their views of immigration. Others were first asked their estimate of the size of the immigrant population and then saw this information in order to make the “correction” even clearer. And some people did not see this information at all.

Here’s what we found. First, the correct information did change people’s estimates of the size of the foreign-born population. In one experiment, we asked people their estimates before and after seeing the information. Those estimates dropped six points among those who saw the information and 11 points among those whose estimates were explicitly corrected.

But this information did not consistently change attitudes about immigration — either people’s perceptions about the consequences of immigration or their views of whether immigration should be increased, decreased or kept at its current level. Most notably, correcting estimates — that is, making them less exaggerated — did not make people more favorable to immigration.

This was also true in one experiment that focused on the local immigrant population and provided correct information about the fraction of the population in the surrounding community.

It was also true in an experiment — discussed in the appendix to our paper — that focused on the undocumented immigrant population, which people also overestimated. But correcting perceptions of the size of this population did not change views about policies toward undocumented immigrants.

The implications of our paper extend beyond immigration. People routinely overestimate the size of many minority groups, including blacks, Latinos, Asian Americans, Jews and gays and lesbians. Our results suggest that correcting the perceived prevalence of these groups would not change views of policies that affect those groups, such as affirmative action or same-sex marriage. It may be that people form attitudes about groups like immigrants for other reasons, and then construct an estimate that more or less rationalizes those attitudes.

However, our results do not suggest that views of immigrants are immune to any kind of information. For example, another study found that a broader package of facts about U.S. immigration — including not only the share of immigrants in the population but also their economic and linguistic assimilation — increased support for immigration.

Thus, to shift public opinion, the most important information about immigrants may not be how many there are, but who they are and what they contribute to our country.