Title: Fairness in Criminal Justice Risk Assessments: The State of the Art,
Abstract: Objectives: Discussions of fairness in criminal justice risk assessments
typically lack conceptual precision. Rhetoric too often substitutes for careful
analysis. In this paper, we seek to clarify the tradeoffs between different
kinds of fairness and between fairness and accuracy.
Methods: We draw on the existing literatures in criminology, computer science
and statistics to provide an integrated examination of fairness and accuracy in
criminal justice risk assessments. We also provide an empirical illustration
using data from arraignments.
Results: We show that there are at least six kinds of fairness, some of which
are incompatible with one another and with accuracy.
Conclusions: Except in trivial cases, it is impossible to maximize accuracy
and fairness at the same time, and impossible simultaneously to satisfy all
kinds of fairness. In practice, a major complication is different base rates
across different legally protected groups. There is a need to consider
challenging tradeoffs.