Now for some good news: according to economic consultant Rick Nevin, this year, the U.S. is on track to experience the lowest murder rate in over 100 years. Nevin reports that, based on preliminary FBI data, the weighted average murder rate in 30 large localities nationwide this year is 18% lower than it was at this time last year. Even in my hometown of Chicago, for example, which has suffered from a sky-high homicide rate, murders have declined by an astonishing 39%, as compared to this time last year. And New Orleans, which in recent years has experienced the nation’s highest murder rate, has seen an 11% decline in homocides this year.

Nevins, like Kevin Drum, believes the decrease in violent crime is attributable to declining rates of lead exposure in childhood. Here’s Drum, referring to curves on a chart which measures the relationship between lead exposure and the murder rate (you’ll have to click on his post to see the chart, because I’m not able to upload it here):

It’s one thing to have two simple curves that match up well. That could just be a coincidence. But to have two unusual double-humped curves that match up well is highly unlikely unless there really is an association. Put that together with all the statistical evidence from other countries; plus the prospective studies that have tracked lead exposure in individual children from birth; plus the MRI scans showing the actual locations of brain damage in adults who were exposed to lead as children—put all that together and you have a pretty compelling set of evidence. Lead exposure doesn’t just lower IQs and hurt educational development. It also increases violent tendencies later in life. If we want less crime 20 years from now, the best thing we can do today is clean up the last of our lead.

Kevin has reported at length on the relationship between lead exposure and violent crime.

The declining murder rate is wonderful news, but it’s no reason to be complacent. Sane gun control laws, of course, would lead to even more significant declines in the rates of homicide and other violent crimes. And unfortunately, a lot of lead is still around. The good news, though, is that lead abatement efforts are wildly cost effective:

Put this all together and the benefits of lead cleanup could be in the neighborhood of $200 billion per year. In other words, an annual investment of $20 billion for 20 years could produce returns of 10-to-1 every single year for decades to come. Those are returns that Wall Street hedge funds can only dream of.

As Kevin writes, “If we want less crime 20 years from now, the best thing we can do today is clean up the last of our lead.”

Kathleen Geier

Kathleen Geier is a writer and public policy researcher who lives in Chicago. She blogs at Inequality Matters. Find her on Twitter: @Kathy_Gee