New from CBKB: A Guide to Calculating Justice-System Marginal Costs

By , May 2, 2013

The costs and benefits of criminal justice policies affect us all—taxpayers, elected officials, practitioners, and society as a whole. As cost-benefit analysts and budget officials know, any meaningful discussion about government costs requires an understanding of marginal costs because these are the costs affected by policy changes.

Because little concrete information is available about how to calculate marginal costs for cost-benefit analyses (CBA) of justice policies or programs, CBKB has published A Guide to Calculating Justice-System Marginal Costs. The new publication is a technical document for analysts and is also intended to inform policymakers who have an interest in the costs and benefits of criminal justice initiatives.

The marginal cost is the amount of change in total cost when a unit of output changes. In the context of the criminal justice system, it is how much the total operating costs of an agency change when workload (such as arrests, court filings, or jail intakes) changes because of a policy or program. The new guide explains each step of calculating marginal costs for corrections, community corrections, courts, and law enforcement. It also provides sample calculations and references to data sources and explains when and why analysts should rely on marginal rather than average costs in cost-benefit calculations.

A Guide to Calculating Justice-System Marginal Costs describes important distinctions among the types of costs that go into a CBA, along with methods for calculating them. You can download the guide at, where you will also find a two-page fact sheet that highlights its key concepts.

CBKB is a project of the Vera Institute of Justice and is supported by the U.S. Department of Justice’s Bureau of Justice Assistance. If you have comments about the guide and how you plan to use it, please post them below. You can also follow CBKB on Twitter and Facebook or e-mail questions or comments to

This post also appears on “Current Thinking,” the blog of the Vera Institute of Justice, which is the Cost-Benefit Knowledge Bank’s parent organization.

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