“For much of the latter part of the twentieth century, New York City was a metaphor for the urban decay confronting America’s cities. With murders topping 2,200 in 1990, New York’s jail population was bursting at the seams, peaking at nearly 22,000 in 1991. Few could have imagined that by 2015, the number of murders in the city would have fallen to 350, with steep declines in other crime categories as well. In 2011, University of California Professor Franklin Zimring dubbed New York City’s crime decline ‘‘the largest and longest sustained drop in street crime ever experienced by a big city in the developed world.’’’