The rise of Donald Trump and Bernie Sanders, many say, is a reflection of the anger in America today.

In numerous polls, voters say America's economy is their No. 1 issue. They believe the middle class is dying, trade is killing U.S. jobs and that their kids won't have a chance to get ahead.

There's some rationale behind their claims.

"The American worker is being left behind," says David Workman Sr. He's "almost 70" and a registered Republican, but he says he'll vote for Sanders. If Sanders doesn't make it to November, he'll support Trump.

"An awful lot of us in the middle class are losing our shirts," says Workman, who is a retired convenience store manager in Coolidge, Arizona.

Trump polls well across the board, but he does best with white men who don't have a college degree and make under $50,000 a year. Sanders also polls best with whites, especially middle class whites.

Here are four key reasons these Americans are so upset.

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1. American families earn about the same as in 1995

There's a lot of confusion about why more than 80% of voters say they're worried about the economy when America is growing and unemployment is so low.

But one look at how much money American families have been taking home in recent years solves the mystery. Family income rose steadily in the 1990s. It dipped a bit after September 11 and the dotcom bubble burst, but then it fell harder.

American households today earn about the same as they did 20 years ago (once you adjust for inflation). That makes it hard to get ahead, especially for indebted families.

Related: U.S. economy better, but Americans aren't feeling it

2. Life is tough for adults without college degrees

Workers without a high school degree are getting left behind in the United States. The jobless rate for workers who haven't graduated high school is almost three times what it is for those with a college degree -- and their wages are far lower, according to the Labor Department.

These workers used to make up the bulk of the manufacturing laborers in America. Some of those jobs have gone overseas or been replaced by machines. While other jobs have been created in the U.S., workers without a high school degree are having trouble transitioning.

It's taking a huge toll, and even driving some to taking their lives. The suicide rate among less educated white men has skyrocketed.

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3. White men's footprint in the job market is shrinking

White men used to feel great about their job prospects. About nine in 10 white men were employed or looking for work in the 1950s.

But since then, white men have faced increasing competition in the workplace. As the Hispanic and female workforce has expanded, white men have steadily dropped out of the job market.

Some have even given up looking for work. The participation rate for white men in the work force has gone down for six decades -- to 72% now from 88% in 1954. Meanwhile, participation for Hispanic men is 80% today. It's only 67% for black men, who have also faced declines.

However, it's still easier for whites to get a job. White unemployment was 4.1% at the end of last year. For blacks it was 8.8% and Hispanics 6.2%.

Related: Buying a home is out of reach in many cities

4. Inequality truly is getting worse

Yes, it's true the rich have gotten richer and corporations are earning record profits. Inequality in America today is now as bad as it was in the 1920s.

The top 10% of income earners in America took half the income made in the United States in 2014.

In 1990, it was 40% and in 1980 that figure was only 35%, according to data collected by Emmanuel Saez, a professor at the University of California, Berkeley, and an expert on income inequality.

Related: 10 reasons single women should be mad

The takeaway

Trump says the American Dream is dead and the country is no longer great. Sanders believes the economy is rigged and the middle class is "collapsing."

In reality, the U.S. economy is a tale of two nations -- not red and blue, but skilled and unskilled.

Skilled workers with college degrees have opportunities for a better life (at least some of them). Unskilled workers face a monumental struggle of competing with the global workforce for jobs. Many of them feel powerless against the force of globalization.

Trump and Sanders have both tapped that anger.