About 70% of Americans consider themselves middle class, according to a 2017 study by Northwestern Mutual. But according to most economists' definitions, that's not possible.

One of the ways the Brookings Institution defines "middle class" is those in the 20th to 80th percentiles of household income. This would make 60% of American households middle class. The Urban Institute defines the middle class as those whose income is from 250% to 499% of the federal poverty line. By this measure, 31% of households were middle class in 2019. And the Pew Research Center, which uses government data to take into consideration household sizes and income, found that 52% of Americans live in a middle-income household in 2018.

Conflating income and class is a mistake, though, some experts say. The reason so many Americans believe they are middle class has nothing to do with income but other cultural indicators. Some broader definitions of the middle class factor in education, occupation, self-perception, or mindset.

Here is how to define middle class, according to an anthropologist, philosopher, and sociologist.

Being middle class 'starts with a kind of cultural place'

Your financial priorities matter more than how much money you make, according to cultural anthropologist Caitlin Zaloom, an associate professor of social and cultural analysis at New York University. Your class status "starts with a kind of cultural place," she says. "It's not necessarily an economic one. We can lead with the idea that class is tied very closely to a particular set of aspirations and whether or not people have the economic capacity to achieve those aspirations."

That means you have to take on debt to achieve certain goals. "The middle class are people who make too much money to qualify for lower-income grants, but make too little to pay for a college education in cash," she explains.

Only considering income, she says, can be misleading: "You can take someone who is an artist and making $15,000 a year, and their family has a lot of wealth — those people are rich."

Another reason an artist from a wealthy family who is making $15,000 is not middle class is because that person's family has likely hit the peak of success. "Fundamentally, one of the things that makes a person middle class is this aspiration for their children to do better," she says. "An artist who has enormous family wealth, it is unlikely that this person's children are going to be doing better than them. They don't have to do better."

The middle class is the 'central pillar to society'

Another reason people might categorize themselves as middle class is because they believe they belong to the most culturally dominant part of a population, says Philipp Rosemann, a professor and chair of philosophy at Maynooth University. "They are precepting that they are the central pillar of society that upholds everything."

Being middle class is less tied to your income and more tied to what freedoms that income allows. Do you have time to look up political candidates and make an educated vote? Do you have time to read the news? Someone who works three jobs and is still below the poverty line probably does not, he says.

As a middle-class American, "you are a representative of the center of society," he says. "You have a voice in the political process. You're not so economically precarious that you feel powerless and completely dependent on gifts from others." Ultimately, if you are in the middle class, you are the norm or the control group.

"The middle class is also the class that sets the tone, culturally, in the country," he says. For example, in years past, mainstream television focused on broadcasting what the average American wanted to see. So the middle class decided how provocative depictions of violence or sex could be.

And, once again, those working many jobs for most hours of their days are unlikely to be watching a lot of television, he says. So their preferences were not catered to.

'Lifestyle distinctions signal who is a member of the middle class'

The middle class is not a monolith, says Karyn Lacy, an associate professor of sociology and African American studies at the University of Michigan. The Black middle class, she says, is composed of three distinct groups: the Black lower middle class, the "core" Black middle class, and the "elite" Black middle class. The latter two groups she calls "blue-chip Blacks."  

Income is one difference among the three groups, she says, but there are also variations in educational attainment, homeownership, and suburban residence. Lower-middle-class people tend not to be college graduates. Elite-middle-class Black people own homes at about the same rate as their white counterparts, she says. And "a majority of the elite middle class live in the suburbs. A majority of the white lower-middle class does too, but only about one-third of the Black lower-middle class does."

"This matters because a suburban residence is a visible signal to others that you have arrived," Lacy says.

It's not only income, education, occupation, and where you live that decide who is middle class. "Lifestyle distinctions signal who is a member of the middle class, too," she says. "Where your children go to school, [...] the kinds of foods you serve for dinner, the type of clothing you wear, the people you vacation with — all these lifestyle choices help to determine who fits into the middle class and who is excluded.

Although Lacy believes that the middle class is not solely defined by income, she says the reason a whopping 70% of people say they are middle class has to do with how Americans want their income perceived.

"Americans don't like to talk about how much money they have," she says. "As a result, almost everyone will say that they are middle class. Poverty is so stigmatized in this country that poor people feel compelled to tell researchers and journalists that they are middle class. The wealthy are often uncomfortable inheriting huge amounts of unearned money, so they, too, will claim that they're middle class."

CNBC