The April jobs report, released on Friday, brought more incrementally good news for the economy: The unemployment rate fell to 3.9 percent, the lowest it’s been since late 2000. “The big thing to me was cracking 4,” President Donald Trump told reporters. “That hasn’t been done in a long time.... We’re doing great.”

But the report also contained a now-familiar disappointment: wages remain stagnant. Average hourly earnings rose by 4 cents over March, bringing the total increase over the past year to just 67 cents, or 2.6 percent. Factoring in consumer inflation, the real increase is close to zero.

This is not how the economy is supposed to work. Pay is supposed to increase during periods of low unemployment, because workers have more power to demand raises from their current employer, or else leave for a better-paying job, while employers have to pay more to retain employees and to compete for new ones. That’s what happened during the jobs boom of the late 1990s, when wages jumped as high as 5 percent annually.

But that hasn’t happened to a meaningful degree today, defying expectations and confounding economists. It’s intuitive that employers don’t like increasing wages, because that leaves fewer profits for them. But economic dynamics like low unemployment are supposed to force their hand. So why have workers not seen the benefits in their paychecks from one of the longest periods of economic and employment growth in history?

It could be due to a variety of factors, but they all point to the same basic idea: Capitalism, as it’s practiced in the United States, has broken economics. Employers have been allowed, through laissez-faire policies, to build up enough power that they’ve become impervious to how economic models dictate they should react.

For example, the New York Times’ Paul Krugman highlighted the possibility that the Great Recession is still depressing wages. Because wages are “sticky”—meaning that it’s hard to cut them even in times of desperation—employers don’t want to increase them in good times, because they know those wages will get stuck at a certain level. “If there’s any truth to this story,” Krugman writes, “the protracted economic weakness that followed the financial crisis is still casting a shadow on labor markets despite low unemployment today.”

In other words, employers have long memories about paying too much for labor during the recession, so they’ll fight as long as they can to pay too little for it in the expansion. And nobody has the power to stop employers from this intentional bias toward underpaying workers. The free market is supposed to correct such imbalances, but it’s failing to do so.

Workers used to have more influence over their employers. But for decades, they have steadily lost whatever bargaining power they once had. This has been true since at least the late 1970s, when worker productivity and worker wages started to drift apart. Employers simply took home more of the profits, and today, not even low unemployment can reverse that.

Unionization is at some of the lowest levels in generations, and collective bargaining has been effectively made illegal in many states. Workers are more atomized than ever. Some are stranded in gig-economy jobs, as independent contractors and “1099” freelance employees. It’s much harder to bid up wages as an independent worker than to get a raise as a salaried employee.

Thirty million workers toil in industries dominated by non-compete clauses, which bar them from moving to work for a competing business. This breaks whatever leverage for wage increases workers might otherwise have, since they cannot shift within the same industry. Employers coordinate with rivals on massive job history databases that, among other things, pinpoint wages, giving management an information advantage to keep salaries down.

Creeping monopolization throughout many sectors of the economy over the past 40 years has exacted a high toll. Recent research from economist Simcha Barkai shows that rising corporate power robs workers of roughly $14,000 in income per year. Monopolized industries capture profits by cornering markets, without needing to share those profits with workers. They don’t have to invest in equipment or jobs to dominate industries where they already have firm control. And they can squeeze workers to accept lower wages, because they have no competition to bid them up. A recent study using data from correlated labor market concentration with a 17 percent decline in posted wages.

Since labor markets are intensely local, there’s also the problem of regional inequality—the abandonment of large swaths of the country, while major cities flourish. Workers in abandoned regions cannot bargain up their wages because they have no alternative while living in areas with scarce jobs. Moving to find work is increasingly difficult given scant savings and inadequate government safety nets.

Finally, economists may underestimate the role of anxiety in modern working life. Wages have been stagnant for so long that average workers have seen significant hits to their living standards. Relatively low minimum wages and easily gamed rules for overtime put low-wage workers in a deeper hole. Retirements are incredibly insecure. Skyrocketing housing and health care costs exacerbate these problems. Many subsist on often predatory debt to cover basic expenses.

This anxiety manifests as despair. Many people of prime working age (25-54) have dropped out of the labor market entirely. If you factor them in, wage growth is consistent with the number of people out of work. But why are these workers sidelined? Untreated drug addiction and mass incarceration are two main culprits, compounded by a severe bias against hiring people with criminal records.

In this environment, holding out for a raise can seem hopeless, or even dangerous. And there’s no indication that a lower unemployment rate will drastically change these dynamics. In fact, if a falling unemployment rate ever caused wages to start to spike, the Federal Reserve would explicitly intervene to reverse the gains and throw people out of work, in the name of “cooling” an “overheated economy” and taming inflation. Stagnant wages isn’t the anomaly, but in many ways the goal.

America, through explicit policies bolstering corporate power and degrading worker power, has gradually altered how the economy behaves, such that even the good times aren’t that good for a majority of people. This is reversible; the policy prescriptions are out there. But it would require nothing less than a revolution in economic policymaking, one that puts workers at the center of the story, rather than adrift on the edges.