Nationally, more Americans live in state prison than in eight states and the District of Columbia. That statement makes it tempting to turn to reports of slowly dropping prison populations for comfort about the state of mass incarceration in this country.

Unfortunately, the big picture is not quite so simple. As counterintuitive as it may seem, if we are ever to get a handle on incarceration in the United States, we need to stop focusing so much on prison populations.

Our overreliance on prison population numbers to diagnose the state of incarceration in this country is based as much on convenience as it is on merit. With millions of Americans churning through the system every year and being processed by hundreds of facilities, official data-keepers are hard pressed to keep up. Most of the data they generate offer limited, highly fragmented views of the overall state of incarceration in this country. But their prison population counts – which include those individuals serving the longest sentences – change relatively slowly and are kept by a single state body. And since population is a metric that most Americans can intuitively grasp – it does not involve any rates, ratios or terms of art – we tend to focus on these statistics and neglect the rest.

Of course, this simplicity is also the source of its shortcomings. While a majority of incarcerated individuals are held in prisons, hundreds of thousands of others are held in local jails. Likewise, since detentions as short as two to three days can be harmful to the individual and to public safety, one need not receive any kind of prison sentence for the ill effects of incarceration to be felt. Further, prisons only tell us about states, while much of criminal justice is done at the county and municipal level.

A more nuanced approach can be found in the Vera Institute’s recent suggestion – and connected data collection project – that we add four additional metrics to our conversation on mass incarceration: jail admissions, pretrial jail populations, convicted jail populations and prison admissions. Each of these numbers, taken on their own, will help shed light on another aspect of the problem. In particular, they will help us understand the gap between rural and urban incarceration rates as well as the role of jails in incarceration.

Even more intriguing, however, is the potential for these new numbers to expand our knowledge even further. Just as a painter with both blue and yellow can also paint in green, these statistics build off each other. For example, once we know a county’s jail admissions and its jail population, we can hazard a fair guess at its average detention length.

Not only would additional statistics expand the scope of our knowledge, they would raise the kinds of questions necessary to extend its depth. For instance, if we know a county’s jail and prison admissions, we gain insight into how harshly the county tends to sentence its defendants. A particularly high ratio of prison admissions could suggest an overcharging problem or, alternatively, that the county has made positive steps to reduce its prosecution of low-level misdemeanors. Either way, such an outlier would deserve further study and could help us figure out additional solutions to over-incarceration.

The ability of data to create value greater than the sum of its parts has also begun to creep more into the public consciousness, spurring some political leaders to start addressing the dearth of criminal justice data in their jurisdictions. Most notably, Florida recently enacted a law that will require each of its counties to collect and make public over 100 pieces of data relating to its criminal justice system. The wealth of information that this requirement will provide has the potential to revolutionize criminal justice in Florida, making the system fairer and more cost-effective – and its communities safer.

Prison population figures are, of course, important. But the days in which they serve as the ‘be all and end all’ of criminal justice system diagnostics needs to come to an end. Only once they serve as first among equals do we have a chance of introducing to reform efforts the nuance and specificity necessary to end our era of over-incarceration.

 

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