When’s the last time someone asked you where you lived or worked, and you answered by naming a police precinct? I’m guessing never. Why? Because while police play a vital role in our communities, we tend to connect more to our neighborhood boundaries than our precinct numbers. (How many of you can even name the number of your home precinct?)

And yet, for as long as modern crime statistics have been recorded here in our city, the police have been delivering those statistics to us, aggregated as counts by precinct number. This type of aggregated data is useful to the NYPD, as it allows them to move resources around according to crime and assess progress, precinct by precinct. But unfortunately, it’s not so useful for the rest of us. Single precincts can cover a wide range of neighborhoods, so even when you hear there is a change in crime levels in your precinct, you might not know if it affects a specific neighborhood. You might want to split crime data up in other ways, like by street or council district, and that has not been possible. Or you might want to know on what days or times of day crimes in a neighborhood occur most often, but with aggregate date, no luck.

But something big quietly happened last week; something that starts to put some of the issues I just outlined to bed. For the first time in its history, the New York Police Department released incident-level reported crime data. That means for each individual reported felony (for the first three quarters of the year), the citizens of New York now have access to data showing where and when that felony was reported instead of a single number telling us the total number that were reported in a precinct over a period of time. There are countless insights to derive within, and with this post I am going to start to scratch the surface.

(Note that location data was only released for six out of seven of the major felony categories- rape locations have been left off to protect the privacy of victims. So for the rest of this post, I’ll talk about the Six Major Felonies, which are the “Seven Major Felonies” that NYC reports, minus rape.)



Before I dive in, it’s worth congratulating the NYPD and the de Blasio administration for making this happen. It’s been a long time coming and I have no doubt that some innovative techniques and insights will arise from this release. Those new ideas will eventually find their way back to our government and make our city even safer. But it’s also worth noting that many other cities (e.g. Los Angeles, Chicago, Seattle, Denver, Boston) provide more granular crime data, with longer histories (many years, instead of just three quarters of data), a broader set of reported crimes (not just six or seven major felonies), and with more detail (has an arrest been made, what are the victim demographics), so as exciting as this moment is, it’s good to remember that New York is still very far behind its peers on police data transparency.

OK, enough context. On to what I learned:

Mapping and Ranking NYC’s Reported Felonies by Neighborhood

The data released is from the first three quarters of 2015, and gave location and time for six major felony categories: Robbery, Murder, Grand Larceny Auto, Grand Larceny of Motor Vehicle, Burglary and Assault. We have had some view on this data in the past – a few years back the NYPD put out its Crime Map, but did not provide access to the underlying data, a BIG Open Data faux-pas. One of the provided map views shows aggregate crime data by precinct, but I chose to redo this sort of analysis at the neighborhood level (well at least Neighborhood Tabulation Area level NYC’s census designated neighborhoods), which is much more granular than precincts.

For each neighborhood, I ranked it against the 188 neighborhoods with NTA’s (removing parks, cemeteries, airports and Riker’s Island). I created a rank for each of the six felony types, where a rank of 1 means that the neighborhood leads for the most of that felony type per resident, and a rank of 188 means the neighborhood has the least of that reported crime per resident. Lastly, I calculated which neighborhood had the highest average ranks versus the lowest. This, in essence, gives each neighborhood an overall felony crime rank, giving equal weight to rankings from each type of crime. (You could argue that weights should be calibrated differently, but we’ll leave that for a future post.) With that, I labeled each neighborhood with its overall felony rank and made the map below:

Clicking on any neighborhood will show you its rank for each of the six felony types, as well as its overall rank (which is also what it is colored by).

Interestingly, the safest seven neighborhoods by this measure are all contiguous in Staten Island and are all fairly low density. It’s also interesting to see that Midtown-Midtown South is ranked 1st overall. This is likely due to the low number of residents in that area compared to the number of people, since each crime rate here is normalized by the population size of the neighborhood.

The top 10 ranking neighborhoods for all felony types can be found in the table below:



While looking at the data, I also noted a few more interesting patterns…



More Robberies Happen in the three hours between 2-5PM, than 2-5AM

One great advantage of disaggregated data is that we can start to explore the time of day that different crimes happen. I know many a New Yorker who is nervous about getting mugged coming home from a late night out. The city certainly feels less safe late at night. But I was interested to learn that the newly released data shows that robberies happen throughout the day, not mainly in the late evenings.

It turns out there are more robberies between 2-5PM then 2-5AM. This fact seems largely due to a large spike on weekdays that begins right after 2PM, seen in the table below, possibly coinciding with school release times, but obviously this warrants much deeper analysis. (Continued investments in after school programs anyone?) Of course there are more people out during the afternoon than early morning, so that does not mean any individual is more likely to be robbed when they are out and about. But nonetheless, it’s an interesting finding which challenged an assumption I had made about New York City. That being said, the most problematic single hour of the week (as opposed to hour of day) seems to be between 4AM and 5AM on Sunday mornings (e.g. late Saturday night), not surprisingly right after all NYC bars close.



Murder and Assault are at Least Four Times More Common in Our Least Affluent Neighborhoods as Compared to Our Most Affluent Ones.

I put each neighborhood into one of five buckets, 1 being the lowest 20% median income income quantiles (those neighborhoods with a median income of less than $34,000) and 5 being the highest (those neighborhoods with a median income of $68,950). I then calculated the felony rates for the residents of each of the five buckets.

For example, the first number in the burglary row is 1.16 meaning that in the least affluent 20% of neighborhoods, the number of burglaries per resident is 1.16 higher than the city average.



Five out of six types of major felonies are more common in less affluent neighborhoods than more affluent ones, as seen by the general lowering of numbers from left to right in the table. The exception is Grand Larceny, which is 1.75 times more likely in the most affluent 20% of neighborhoods. The 1 to 5 Ratio numbers on the right of the table tell you how much higher the reported felony rate is in the least affluent 20% versus the most. The numbers that stand out are Murder and Felony Assault, which are more than 4 times more likely in less affluent neighborhoods. Of course it’s no surprise that crime is higher in less affluent neighborhoods, but quantifying it this way shows just how much in a more digestible form. This was not generally possible to understand before last week’s open data release, as census data is not usually collected by police precinct.



Conclusion

There is so much more to do with this data, but in order to do a meaningful analysis, the public needs access to more than one year of crime data, and other reported crimes besides major felonies. As noted, many other cities are providing just that. Just today, the de Blasio administration proudly proclaimed that 2015 was “the safest year in the modern history in New York City”, and yet they are holding back the very data that can back up that claim with more specificity. That is truly unfortunate, but the good news is we are seeing transparency for the first time in our history . And that is a win for all New Yorkers, including those that work at the NYPD. Thanks again to all that made this happen (with a special thanks to The Transparency Working Group, The Mayor’s Office of Data Analytics and DoITT who worked behind the scenes).



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-Crime data can be found here.

-Neighborhood Tabulation Area Boundaries are here.

-Median Income and Population of those boundaries are here.

-Analysis done in Excel, QGIS and IPython

-Interactive map made in cartodb