Did Stop and Frisk Work?

I don't have time to fact check every statement that was made by both Trump and Clinton at last night's presidential debate. I really don't need to since there are plenty of people out there who are. I do have time to share data I already have. And what I already have pertains to this moment from Trump.

Now, whether or not in a place like Chicago you do stop and frisk, which worked very well, Mayor Giuliani is here, worked very well in New York. It brought the crime rate way down. But you take the gun away from criminals that shouldn't be having it.

About a year ago, I pulled crime rates for the top five largest cities in the United States, plus the national average for the years 1985 to 2012. The data comes from the FBI's Uniform Crime Reporting Statistics. The FBI apparently has data for 2013, 2014, and 2015. It's just not available in this database. For 2014 and 2015, I have some data collected by fivethirtyeight.com. I need to update my data set, but the years I need aren't relevant to the current question.

The current question is this: did stop and frisk have any affect on violent crime rates in New York City?

Let's start with Murder and non negligent manslaughter. The chart below summarizes the data. I've highlighted the years that stop and frisk policies were in effect.

In looking at this chart, two things jump out at me. First by the time stop and frisk was in use, the crime wave in New York City had largely receded. The second thing I notice is that crime rates were down for the other four top cities as nationally. (The average shown in the chart is for the top 60 U.S. cities, not just the top five. This means that crime went down everywhere regardless of policy.

What remains now is to see if these patterns hold true for other types of crime. That's a task for a different evening. It's getting late and I have a day job.