On any given day, about 9,200 men and women are held in New York City’s jails. 

Most of them are housed on Rikers Island, which is notorious for its deplorable conditions and history of violence. The mayor, the city council, and the Independent Commission on New York City Criminal Justice and Incarceration Reform have recommended closing Rikers Island and replacing it with smaller jails in the city’s five boroughs. Everyone agrees that in order to do this, the city must reduce the jail population by nearly half—to 5,000.

A key question for those planning the future of New York City’s jail system is this: “When will we get to 5,000?” Fortunately, we can keep tabs on the impact of reforms. The New York City Department of Correction’s publicly available Daily Inmates in Custody dataset allows users to track the city’s jail population in close to real time.

This dataset is updated daily and made accessible through NYC Open Data. For each person in custody, the Department of Correction reports more than ten data points. You can get basic demographic information about who is in custody (age, race, gender, gang affiliation, and mental health status). You can find out, on any given day, how many people are in jail pretrial, sentenced, on a technical parole violation, or waiting to be transferred to state prison. You can see the breakdown of who is in jail based on charge by penal code. You can even tell whether or not individuals have committed infractions during their jail stays.   

This data is amazingly detailed, but it is also a little unwieldy in its raw form and gets overwritten every day. So I developed an interactive dashboard called JailVizNYC that allows people to easily filter the data, view population trends by saving the data each day, and explore in detail the charges most frequently holding people in jail at the misdemeanor, non-violent felony, and violent felony levels.

The dashboard can also be used to explore four key points in the criminal justice system where reforms are needed to get to an average daily population of 5,000: arrest, arraignment, case processing, and sentencing.

The dashboard can be used to identify appropriate cases for diversion. For example, the dashboard reveals that on November 6, 2017, there were 358 people in jail booked on low-level, misdemeanor charges like drug possession (including marijuana) and petit larceny who could be diverted. The data also lets us see what would happen if supervised release or alternative forms of bail were used more often. Take that same date: November 6, 2017. If the city were to divert all misdemeanors and nonviolent felony arrests to supervised release or use alternative forms of bail, we would have seen an additional 2,650 fewer people in jail on that day.

The city can make a lot of progress reducing the jail population through expanded diversion efforts, but to get to the goal of 5,000, it must also reduce the time that people held on bail spend in custody. As of November 6, 2017, 3,384 people in city jails were held pretrial who had been charged with a violent felony offense. On average, these individuals stay in jail 250 days while awaiting trial. If the city reduced average length of stay by only seven days, we would see at least 47 fewer people in jail. And if the time spent in jail was reduced by 14 days, that number would increase to at least 95.

To reduce the city’s average daily jail population to 5,000 will require multiple strategies. JailVizNYC helps make sense of the vast amount of jail data New York City makes publicly available, giving policymakers and practitioners even more tools to make that 5,000 number a reality.

To track the impact of these reforms and to explore the data, visit https://vera-institute.shinyapps.io/nyc_jail_population/