Labor Day is set aside to honor the American worker who helped build the world’s strongest economy on the principles of shared prosperity and equal opportunity for advancement.

So, it’s ironic that while millions of us will enjoy a paid day off, millions more will be hard at work in restaurants, stores and medical facilities, and caring for children or the elderly in homes, working long hours for little money with little hope of getting ahead.

This is the state of the working class in a post-industrial America, where globalization and technology have swallowed up manufacturing jobs while the demand for services has increased. The growing reality is that the jobs which employ the most people — and the ones that are projected to grow the most over the next decade — are in sectors like food, retail, customer service and health, not in the mills or factories that created a blue-collar middle class that we celebrate on Labor Day.

Understanding this new working class and representing its interests will be the challenge of our time for policy makers in government and the labor movement. Only when these jobs can support stable families that will nurture children who take full advantage of educational opportunities will we see the kind of economy that most Americans want.

There is no absolute definition of working class, but one clear line of demarcation is attainment of a college degree. Most of us know an exception — like a well-educated person who does manual labor or a successful business operator who never finished high school — but a college diploma is a prerequisite for most middle class work.

Much of the conversation about building the middle class has centered around making higher education more available, and rightly so. The earnings gap between graduates and non-graduates has been growing for decades.

But less than one-third of Americans have a four-year degree, and even if there were a massive public investment made to significantly increase the number of graduates, there would still be many more people without diplomas than with them.

And there is work for those people. Service jobs cannot be sent offshore, and most can’t be replaced by robots. As baby boomers reach retirement age, there is increased demand for personal care aides, home health aides, and nursing assistants, as well as a wide range of hospital aides and assistants — all jobs that do not require more than a high school diploma.

Who fills these jobs? According to “Sleeping Giant: How the new working class will transform America,” by Tamara Draut, many are women. Two out of three non-college educated women are in the workforce, compared to half in 1980. These jobs are also much more likely to be filled by someone who is black, Hispanic or Asian, especially if you look at the youngest segment of the workforce, where 47 percent of employees are minorities.

And contrary to popular opinion, these jobs are not filled by teenagers working for pocket money. On average, minimum-wage workers, a subset of the working class, supply at least half of their family’s income.

Many of these workers earn so little that they qualify for government programs, such as food stamps and rental assistance. They rarely earn paid time off when they are sick or need to care for a family member. They are rarely represented by a union.

The policy implications are clear. These jobs are essential, and the people who fill them deserve to have the dignity that comes with making an honest living. That means a higher minimum wage, earned paid leave and access to affordable health insurance among other protections.

The emerging awareness that these workers share common interests should lead them to organize so they will have a stronger voice where they work and in the political arena.

It was that kind of activism that brought us the end of child labor and the introduction of the eight hour day. It also gave us the holiday we celebrate every year on the first Monday in September.