New research finds we believe class boundaries are more porous than they are in reality.

America, we learn as children, is the land of opportunity—a place where anyone who works hard and saves their money can climb their way into a higher social class. While statistics do not bear out this belief, newly published research suggests it remains stubbornly entrenched in our minds.

Across four studies, Americans offered “substantial and consistent overestimates of class mobility, overestimating the amount of income mobility and educational access by a wide margin,” write University of Illinois psychologists Michael Kraus and Jacinth Tan.

In the Journal of Experimental Social Psychology, they report some Americans—young people, conservatives, and, unsurprisingly, members of the upper class—are more likely than others to hold unrealistic views on this subject.

“Participants underestimated the extent that students the from top universities are from the top 20 percent of income families, suggesting again that (they) overestimated the extent that universities are open to Americans from lower income levels.”

But they add that these differences “ranged from small to medium in magnitude.” The rags-to-riches notion is embedded in our basic mythology, and, for better or worse, most all of us believe it is far more common than it is in reality.

One study featured an online sample of 751 American adults. After providing information regarding their annual income, education level, and political leanings, they were “asked to think about 100 people” and estimate the likelihood they made a series of significant life changes between 1997 and 2006. Their guesses were compared with actual statistics from that decade.

“Participants overestimated the extent that people actually move up in wealth,” the researchers write. Specifically, they overestimated “the extent that working 1,000 extra hours would improve their income standing; the number of individuals who would move from the bottom 20 percent to the top 20 percent of income; the amount that (attending) some college would move people out of the bottom 20 percent of income; and the number of students from the bottom 20 percent of income families at top universities."

“Participants also underestimated the extent that students the from top universities are from the top 20 percent of income families,” the researchers add, “suggesting again that (they) overestimated the extent that universities are open to Americans from lower income levels.”

So why are we so far off, overestimating class mobility by nearly 23 percentage points over the four studies? Kraus and Tan point to a combination of “informational errors” and certain psychological needs. “Overestimates of class mobility satisfy the need to believe that the societal status of (oneself) and others is determined fairly and justly,” they write.

To address that last point, in another study they asked 747 American adults recruited online to make those same guesstimates about education, work, and mobility. But in one version of their questionnaire, the wording was changed slightly; participants were asked to make their estimations for individuals who “are similar to you in terms of goals, abilities, talents, and motivations.”

Once again, class mobility was greatly overestimated. More importantly, the difference between participants’ beliefs and reality was larger when they were considering the likely fates of people like themselves. Even if we don’t believe everyone can make it big, we do believe we—and others like us—have what it takes.

This belief has its benefits, of course. Another recently published study found that working-class individuals had poorer health than members of the upper class, but only when they believed class differences are rooted in biology. Belief in upward mobility apparently buffered them from physical and emotional problems.

Nevertheless, for politicians and policymakers, a realistic view of class stratification would seem to be a necessary prerequisite for designing social programs—not to mention a genuinely fair tax structure. Teaching kids they can make a better life for themselves is a good thing, but only if the resources that could enable that sort of rise—such as quality public schools for all—are actually in place, and functioning effectively.