In the U.S., “middle class” is not just an income category. It’s a cultural norm.

That is why people get upset when they read reports that the middle class’s share of total income is shrinking. And it is one reason we get into such vicious debates about what it means not to raise taxes on the middle class. Almost all of us believe we should be among the exempt.

A recent Pew Research Center survey asked people to classify themselves as upper class, upper-middle class, middle class, lower-middle class or lower class. The results were nothing like the neat income quintiles that economists and Census Bureau reports use. Forty-nine percent called themselves middle class, 15 percent upper-middle class, and 25 percent lower-middle class. With a few gradations, in other words, 89 percent of Americans identify with the middle class.

Politicians want to make sure everybody has a chance to be middle class -- and, equally important, that all people who think of themselves that way feel appreciated and protected. So if a middle-class lifestyle includes owning a home or going to college, policy entrepreneurs find a ready audience for ideas designed to make those goals easier to obtain -- with results that are, at best, mixed.

Secure Jobs

Here, another result from the Pew survey suggests potential dangers ahead.

The poll asked whether Americans need certain things to be considered middle class. Forty-five percent of respondents said it is necessary to own a home, 37 percent said you must have a college education, 66 percent said you need health insurance -- the most recent focus of expansive public policy. A whopping 86 percent said you have to have “a secure job.”

Not “steady work” or “a reliable income” but “a secure job.”

Working for a living has long defined the middle class, as opposed to rentier aristocrats or the dole-dependent or profoundly insecure poor. But a lot of other assumptions are baked into the term “secure job.” It seems to exclude from the middle class everyone who doesn’t draw a regular paycheck from a single organization -- the self-employed (about 11 percent of the workforce), the retired, housewives, students -- as well as employees on limited-term contracts. As a self-employed writer who doesn’t have “a job,” let alone a secure one, I found the word choice striking.

“The wording ‘secure job’ means a steady or stable job,” says Wendy Wang, a research associate on Pew’s Social & Demographic Trends project. A comparable survey in 1991 used the phrase “white collar job” and not surprisingly drew a much lower positive response: about 30 percent. Pew researchers decided to change the wording and, in doing so, picked a term that reflects the times. “Job security is something that the middle class may be concerned about these days,” Wang says.

That concern represents a significant change since the onset of the recession. Contrary to many news-media claims, U.S. employees had enjoyed several decades of rising job security before the 2008 crisis. In a 2008 American Economic Review article, economist Steven J. Davis of the University of Chicago’s Booth School of Business examined many different data sources and found the same pattern in all of them: “American workers face lower risks of job loss in recent years than 10, 20, or 30 years earlier.” That security has now disappeared, and people are anxious.

In polls since the 2008 financial crisis, Gallup Inc. has found that about 30 percent of workers were worried about being fired or having their wages or hours reduced. Over the previous decade, the numbers never topped 20 percent and were usually lower.

Employee Protection

Suppose policy makers decide to follow the polls and try to guarantee everyone “a secure job” in order to promote the middle class. If the economy remains sluggish and the public anxious, it is easy to imagine a turn away from the current focus on job creation toward a new emphasis on job security. This seems particularly likely in a second Barack Obama administration that would be looking for initiatives that don’t add to federal spending. We might see regulations, for example, to make it harder to fire long-term employees. The Obama campaign has already excoriated Republican nominee Mitt Romney for job cuts when he was at Bain Capital Partners LLC.

To see the potential results of such policies, you don’t have to look to Europe’s persistent unemployment. You just have to dream a little.

Imagine a career in which once you had worked somewhere for a long time -- say, seven years -- and you couldn’t be fired unless you did something really horrible. To make the picture even more appealing, imagine further that your industry was largely immune from foreign competition, had been enjoying increasing consumer demand, was subsidized by the state and federal governments, and rarely experienced any bankruptcies.

As you have probably realized, this career exists. It’s the professoriate. But while outsiders imagine higher education as a sheltered enclave of secure jobs, the actual state of American faculty members is much more uncertain. Tenure-track employment is no longer the norm. Part-time work is.

About 30 percent of faculty members are either tenured or on the tenure track, compared with about 57 percent in 1975. The rest are “contingent faculty”: About 19 percent work full time, usually on contracts lasting one to three years, and more than half work part time. (These figures omit graduate students who also teach classes.) Along with a lack of job security, contingent faculty members receive lower pay and fewer, or no, benefits. They frequently don’t have offices and may not even get library cards.

It’s a two-tiered system that depends heavily on people whose main jobs are doing something else. And it is what you get when you guarantee permanent employment but need flexibility as conditions change. How well it works for academia depends on whom you ask. But it certainly doesn’t deliver secure jobs.

(Virginia Postrel is a Bloomberg View columnist. She is the author of “The Future and Its Enemies” and “The Substance of Style,” and is writing a book on glamour. The opinions expressed are her own.)

To contact the writer of this article: Virginia Postrel at vp@dynamist.com

To contact the editor responsible for this article: Tobin Harshaw at tharshaw@bloomberg.net