More than a quarter of black Americans are poor. But the majority of poor Americans are white. These two facts tell us a great deal about the gulf separating the worlds of black and white in America. They also explain how unsurprising it is that current race relations have led to the killings of blacks by the police and of the police by blacks. Finally, they explain the resurgence of the exploitation of race hatred for political advantage by white demagogues.

Let's begin with numbers that do not lie. According to the U.S. Census Bureau, of the 36 million black Americans in the last official count, 9.4 million or 26 percent fell below the official poverty line of $23,550 in income for a household of four in 2013. The same survey found almost 26 million white Americans living in poverty, about 12 percent of the total.

In other words, more than twice as many whites as blacks were poor in absolute number. But in proportion to population, about 1 in 10 whites were poor, compared with 1 in 4 blacks. In 43 out of 50 states and the District of Columbia, black poverty exceeded 20 percent; in four states (Iowa, Maine, Mississippi and Wisconsin), black poverty rates were over 35 percent.

Research in 2014 by Stanford University economics Prof. Raj Chetty using tax data found that areas in the U.S. with greater income inequality also have less upward mobility for children from low-income families. This is the so-called "Great Gatsby Curve." In Charlotte, N.C., for example, a child whose household ranks in the lowest fifth for income has less than a 5 percent chance of reaching the top income fifth in his or her lifetime.

Middle- and upper-middle-class white Americans remain largely removed from the black poor (forget about the rich, who don't encounter poor blacks except on the freeway or as servants). But poor whites, even if they do not live with or near the black poor, compete for low-paying jobs with them and are much more likely to be affected by violent crime, regardless of its racial origin.

The poor — both white and black — are trapped by the Gatsby Curve on the bottom, looking up with little to hope for and much to fear.

Since (and despite) efforts at desegregation beginning in the 1960s, the poor of both races have thus been slowly left further and further behind. The festering resentment of poor whites has been fertile ground for the seeds of reaction. Thirty years ago, as affirmative action began to lift blacks into previously white educational and business positions, it was the black middle class that was most able and prepared to take advantage of these opportunities, while the black poor mostly stayed where they were. Poor whites, meanwhile, wondered why they were deemed less worthy of the attention given to blacks who were already one step ahead of them, and their hatred began slowly to burn.

As white supremacist and Donald Trump admirer David Duke said: "Affirmative action is a very nice term for racial discrimination against better-qualified white people in jobs, employment, promotions and scholarships, and college admittance."

One place where the lower-middle-class police and poor blacks meet is on the streets in black neighborhoods and on the road in inner-ring suburbs like Falcon Heights in the Twin Cities. The nation's police forces are mainly white. According to a New York Times investigation in 2015, the percentage of whites on the police force is more than 30 percent higher than the communities they serve in hundreds of police departments across the country.

Ronald Weitzer, a sociologist at George Washington University, observed: "Even if police officers of whatever race enforce the law in relatively the same way, there is a huge image problem with a department that is so out of sync with the racial composition of the local population." In the Cleveland inner-ring suburb of Maple Heights, for example, near where the Republican National Convention was held last week, the police force is 70 percent more white than its residents. As the Times noted, like Ferguson, Mo., Maple Heights went from being mostly white to two-thirds black in the past decades, and the race gap in policing remains despite an affirmative action deal to hire more minorities.

The average police officer makes about $28,000 a year, according to the employment website Indeed.com, although the Bureau of Labor Statistics puts the average higher when more categories of police work are included. This is above the poverty line, to be sure, but barely touches the top of the lower middle class. The police and blacks in poor neighborhoods coexist uneasily, pitched together in a cauldron of suspicion and violence that economic disadvantage brings, in varying degrees, to both of them.

White demagogues understand this volatile mix of race alienation intuitively, even if they are born of privilege. They know they need not call out racial slurs explicitly, like Klansman Duke, and may even seem to disavow him. All they need is a gesture or two in the right direction, and the haters will come running. Duke has been cleaned up, unrobed and re-attired in a Brioni suit. As the late Walker Percy, Southern novelist and student of race politics, told the New York Times in 1989 about Duke's election to the Louisiana House: "He's not just appealing to the old Klan constituency, he's appealing to the white middle. And don't think that he or somebody like him won't appeal to the white middle class of Chicago or Queens."

The bitter truth is that America is not (and perhaps never has been) a land of opportunity for the poor. For those trapped on the bottom, the fruits of poverty — hatred and violence and demagoguery — are not surprising at all.

Carlisle Ford Runge is Distinguished McKnight University Professor of Applied Economics and Law at the University of Minnesota. This article reflects his views and not those of the University of Minnesota.