Instead of a tough-talking mayor, new windows may be to thank for the drop in violent crime in New York City. The Washington Post reports that according to economist Rick Nevin, 65-95% of the variation in violent crime in 9 countries can be explained by lead. Nevins claims that crime rates rise and fall approximately 20 years after environmental lead concentrations increase and decrease, respectively. This theory isn’t new, but its relation to American politics is. Rudy Giuliani, former New York City mayor and current presidential candidate, claims that his law enforcement policies reduced homicides by 67% and total crime by 57% during his tenure as mayor from 1994-2001. Nevins argues that Giuliani benefited from policies in the 1960s to replace old lead windows (to reduce deadly falls) and in the 1970s and 1980s to reduce lead in paint and gasoline.