A GAO report has found that ICE could improve its cost estimates on immigration detention.
ICE bases its budget request for detention resources on guidance from OMB and DHS. To project its detention costs, ICE primarily relies on two variables: the average dollar amount to house one adult detainee for one day (bed rate) and the average daily population (ADP) of detainees.
GAO found some inconsistencies and errors in ICE’s calculations for its congressional budget justifications (CBJs). For example, in its fiscal year 2015 budget request, ICE made an error that resulted in an underestimation of $129 million for immigration detention expenses. While ICE officials stated their budget documents undergo multiple reviews to ensure accuracy, ICE was not able to provide documentation of such reviews.
ICE consistently underestimated the actual bed rate due to inaccuracies in the model, and it is unclear if the ADP used in the budget justification is based on statistical analysis. GAO identified factors in ICE’s bed rate model — such as how it accounts for inflation and double counts certain costs — that may lead to its inaccurate bed rate projections. For example, in fiscal year 2016, ICE’s projections underestimated the actual bed rate by $5.42 per day. Underestimating the bed rate by just $5 per day can lead to an underestimated budget request of more than $62 million.
ICE’s methods for estimating detention costs do not fully meet the four characteristics of a reliable cost estimate, as outlined in GAO’s Cost Estimating and Assessment Guide. For example, while ICE’s fiscal year 2018 detention cost estimate substantially met the comprehensive characteristic, it partially met the well-documented and accurate characteristics, and minimally met the credible characteristic.
GAO recommends that ICE documents and implements its review process and assesses and updates its adult bed rate methodology. It also recommends that ICE determines the most appropriate way to project the ADP for use in the congressional budget justification and document the methodology and rationale behind its ADP projection, and ensures its budget estimating process more fully addresses cost estimating best practices.