https://www.scientificamerican.com/article/income-inequalitys-most-disturbing-side-effect-homicide/

Income inequality can cause all kinds of problems across the economic spectrum—but perhaps the most frightening is homicide. Inequality—the gap between a society's richest and poorest—predicts murder rates better than any other variable, according to Martin Daly, a professor emeritus of psychology at McMaster University in Ontario, who has studied this connection for decades. It is more tightly tied to murder than straightforward poverty, for example, or drug abuse. And research conducted for the World Bank finds that both between and within countries, about half the variance in murder rates can be accounted for by looking at the most common measure of inequality, which is known as the Gini coefficient.

The murders most associated with inequality, it seems, are driven by a perceived lack of respect. Like most killings, these are mostly perpetrated by males—and in societies with low inequality, there tend to be very few murders. To an outsider, these deaths, which make up more than a third of the homicides with known motives reported to the FBI, seem senseless: a guy looks at someone else the wrong way, makes a disrespectful remark, or is believed to have winked at another man's wife or girlfriend. These incidents seem too trivial to be matters of life and death. “A prosperous guy like me, if someone [insults me] in a bar, I can roll my eyes and leave,” Daly says. “But if it's your local bar, you are unemployed or underemployed, and your only source of status and self-respect is your standing in the neighborhood, turning the other cheek looks weak, and everyone soon knows you are an easy mark.”