In 2015, total drug-related arrests dropped to the lowest level in three decades, a Chicago Sun-Times analysis of city crime data found.

And the rate of drug busts plunged more sharply in the first four months of 2016. Chicago Police are on pace to make 13,000 narcotics arrests by year’s end. That would be the smallest annual tally since 1973, two years after President Richard Nixon declared a national war on drugs.

Police and prosecutors say cops have been less aggressive on the street since the November release of the dashcam video showing 17-year-old Laquan McDonald shot 16 times by Officer Jason Van Dyke.

But the downturn in drug arrests began long before then. And while police are making fewer arrests for other offenses, the number of narcotics busts has fallen faster — by nearly half between 2008 and 2015.