And yet when we compare state homicide rates in "dry" and "wet" years, the 40 percent jump in homicide rates drops to 26 percent.
Higher immigration was associated with reductions in homicide rates for white, black and Latino victims.
The increase in homicide rates has a strong social impact regarding neighbourhood security.
In fact, depending on the model, the actual effect of going dry ranges from a 5 percent increase to a 13 percent decrease in state homicide rates, with margins of error of 4 percentage points.
Both have seen substantial decreases in their homicide rates since reaching peaks in the 1990s.
And some of the aid does work: There is good evidence that violence-prevention assistance to El Salvador has contributed to a decrease in the homicide rate, a likely factor behind the drop in migration to the United States.
In his exhaustively researched 2012 book, "Great American City," Sampson noted that, in Chicago, "increases in immigration and language diversity over the decade of the 1990s predicted decreases in neighborhood homicide rates".
A November 2011 study by the Rand Corporation found that, on average, every 10percentt increase in the size of a city's police force led to a decrease in the homicide rate by 9percentt, robbery by 6percentt and car theft by 4percentt.
Although the gender gap had decreased to 7.6 years in 2010 [ 2], mainly due to the reduction in the homicide rates among men, the mortality differences between sexes are still excessive.
The group's findings also align with a study published in the Journal of American Medical Association earlier this month, which found that "laws that strengthen background checks and permit-to-purchase seemed to decrease firearm homicide rates". .
