"Daly says that no one knows what time lag to expect between a rise in inequality and a rise in murder – but if it does take a few decades, this could be the start of a troubling trend, not a blip."
Income inequality rose, and homicide rate rose, then income inequality rose much faster and homicide rate dropped dramatically.
Surprising, really?
Economic disparity causes violent crime. To believe you can accept and encourage one without also accepting and encouraging the other is ignorant, childish, and utterly irrational.
(the book 'Nine Crazy Ideas in Science' in chapter 1 cites a bunch of the research done in this field, they were specifically looking for the influence of overall gun ownership rates but found gun ownership prevalence has no predictive power for violent crime rates)
So the use of tetra-ethyl lead in vehicle fuel from 1920 to 1975 in the US roughly correlates with greater nationwide violence between 1942 and 1997. Specific tracts known to have ongoing lead contamination problems show stronger correlations.
So if lead pollution had not been tackled in the 70s, poor people in the alternate-timeline 2017 might be even more murdery, now that wealth imbalances are worse. Their opioid epidemic might look more like the 1980s crack epidemic.
I know that hookworm played a significantly role in the US south, and after its eradication things improved every single year since. Hookworm is still a major problem in most of Africa, though. Infection with hookworm in childhood results in permanent IQ loss, regardless of whether it is later treated, the damage remains.
My personal opinion is that we should not necessarily expect the actual monetary scale of the difference to accurately predict the magnitude of the violent crime. Most likely, the economic disparity is a proxy for something else that does not scale the same as the monetary values do. Namely control. Economic disparity always coexists with a small group exerting control upon a larger one to extract the value they create and take it for themselves. Humans always respond negatively to control - both being controlled and exerting control on others. They react pretty predictably, too. They assert control over themselves and their own bodies, then seek to establish status by being seen as dominant in their peer group, then seek to establish an alternative power hierarchy from the overaching order, then engage in plays for dominance between those alternative hierarchies (gangs), then eventually the gangs merge and become an army who goes to war against the overarching order. It happens in families, in schools, in prisons, in militaries, in nations, everywhere. Different scales, and different manifestations, but control is a poison to humans.
