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What Jail Population Projections Tell You About a Government’s Aspirations

Michael Jacobson and Victoria Lawson

March 12, 2024

Governments can shape conditions that determine

Governments can shape conditions that determine

how many people need to be incarcerated.

One of the many essential roles of local government is to run and operate jail systems which primarily incarcerate pretrial detainees, people who have not been found guilty of any crime. The deprivation of liberty is a hugely consequential judicial decision given that even short jail stays are potentially harmful to those who are incarcerated in terms of their physical and mental health and other negative impacts that go along with separating people from their communities, family and work. As a result, these systems should be used with great parsimony, holding only those who present a significant public or community safety threat or who are at high risk to flee. Other than those two categories, nobody else should ever be in any jail system in pretrial status. (We note that New York State is unique in the nation in limiting the permissible bases on which a judge can deprive a person of his or her liberty pretrial to a consideration of whether the person will return to court.)

Given that, a fundamental question for any local government is: What is the right size of a jail system? This is not a theoretical question. All over the country, policymakers must decide whether they need more or less capacity now and in the future. Whether it is replacing an aging jail, reducing capacity due to underuse, trying to figure out the impact of new laws that can affect jail populations or creating a new system from scratch (which perhaps best describes the situation New York City finds itself in), projecting jail populations into the future and then building (or downsizing) to those projections has enormous real-world implications. Overbuild, and these governments will wind up needlessly spending huge amounts of scarce capital and expense dollars. Underbuild, and the same governments will be forced to create emergency capacity (which is almost always expensive, temporary and can be dangerous for those incarcerated as well as for staff). 

The answer to all these questions lies in accurately projecting the need for jail beds into the future. While the methodological details of projections are of course important (how many historical data points are used, for what time periods, using what statistical techniques, etc.), the heart and soul of these sorts of projections are the policy, legal, demographic and operational assumptions that are made about what the future holds and how all these will affect the need for jail capacity. 

The two primary drivers of jail populations are admissions, or how many people enter the jail, and length of stay, or the amount of time that people are detained in jail either pretrial or on a sentence of less than one year. An accurate projection, then, needs to consider the factors that drive admissions and length of stay. Local population trends (e.g., changes to migration rates, the percentages of young people), crime and arrest rates, physical and health characteristics of people in custody, proposed legislative changes to the penal code and how local court systems operate and process cases all serve to drive the ultimate size of any local government’s jail population. 

While we recognize that systemic reform is a serious challenge both substantively and politically, particularly given the multitude of agencies and even multiple branches of government involved, it is both possible and necessary.

All who engage in this work should accept one simple and basic premise, and that is that recent or even long-term trends influencing these two factors are not immutable. They are malleable. That is, in projecting a jail population that will serve as the basis for a significant financial investment (in New York City’s case, also a sea change in how jails are designed, built and operated), it is incumbent on local policymakers not to simply accept trends that reflect inefficiencies or injustices, whether those are related to court processes, the overuse of bail or gaps in the system of providing alternatives to jail for those with serious mental illness, to name a few. Put another way, if policymakers smartly address the underlying forces that shape admissions and length of stay, they can not only predict future jail populations, but help control them.

City governments and their elected leaders are not powerless to reform these built-in inequities, inefficiencies or gaps in services. While we recognize that systemic reform is a serious challenge both substantively and politically, particularly given the multitude of agencies and even multiple branches of government involved, it is both possible and necessary; not doing so is antithetical to the fiduciary responsibility that comes with governing cities. Making it happen will require commitment and political will — especially, in New York City’s case as a strong-mayor jurisdiction, from the mayor.

What, then, is the right balance to strike in making assumptions about how much improvement is likely to happen, assuming there’s a basic commitment to reform, over a multi-year period? A lot rides on those assumptions. Should a jurisdiction assume that, at the end of the day, reform is just too difficult to achieve because current practices are so baked into the fabric of how the system operates? If so, then the projection will effectively accept that all of these inefficiencies will exist and will likely get worse into the future. That is of course the most “conservative” assumption and will result in the largest and most expensive jail-building and -operating program. It is also the approach that the city has taken to date, according to the Department of Correction’s projection shared in response to Vital City’s FOIL request.

Even if the city pulled back its support for closing Rikers, making the system as small as possible should be a categorical imperative both to limit its harm to New Yorkers and to curb the out-of-control spending associated with the current system.

On the other end of the spectrum, a jurisdiction could decide that, through its efforts and in a relatively short period of time, the system can be totally transformed into a national model of best practices and efficiency in terms of the speedy disposition of justice and the maximum provision of community-based services that can safely divert people from jail. This would of course result in the smallest and least expensive jail-building and -operating program. But being too credulous has its downsides, because it can leave a city dangerously unprepared when reality rears its head.

Neither of these relatively extreme positions presents a feasible path forward. Simply accepting the inefficiencies and inequities that exist now is contrary to the fiscal, governance and humanitarian aims of government. On the other hand, building projections that assume all the wished-for reforms are somehow put into action is unrealistic and irresponsible, especially given the relatively short time period in which reforms must be realized, the limited tax dollars available and the multiple pressing needs on those dollars. 

The “art” of the projection is answering the question of where the sweet spot is between the aspirational and realistic. Here, we provide a consolidated list of the key recommendations for reducing the population made across the articles in this issue.

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Ultimately, the city must decide which specific reforms to pursue (although as we have argued in this issue, it is absolutely imperative to prioritize the issue of the growing and harrowing lengths of stays in New York City). But failure to consider and include these and any other available options in any jail population management strategy simply falls short of any responsible and legitimate effort to fulfill its legal and moral mandate to close Rikers for good. 

Even if the city pulled back its support for closing Rikers, making the system as small as possible should be a categorical imperative both to limit its harm to New Yorkers and to curb the out-of-control spending associated with the current system. For that reason, we presume that the mayor will make these reforms a priority and be willing to spend whatever political capital it takes to make sure that they are realized — even in the branches of government that are outside his formal control. At the same time, any responsible and legitimate effort to project the future size of the jail population must include systemic reform and include an implementation and accountability plan for achieving those reforms. Failure to do so — taking inaction as a foundational premise, as the current city projection produced in response to Vital City’s FOIL request seems to do — is at best inadequate and at worst disingenuous, creating the impression that the city bears no responsibility for and has no control over the size of its jail population. Beyond that, building reform into the projection is in itself a powerful tool that the city can use to actually bring about change. By doing so, it can keep the pressure on itself and all the branches and agencies of government that are going to be constrained by the ultimate capacity of the jail system and hold them all to account for making these reforms a reality.