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COMPAS and Bias in Recidivism Algorithms

COMPAS (Correctional Offender Management Profiling for Alternative Sanctions) is a commercial risk assessment tool from Northpointe, now Equivant, that scores how likely a defendant is to reoffend.

  • 4 min ka
  • kẹhin imudojuiwọn
Lori iwe yi4 min ka
  1. Akopọ
  2. Jin Dive
  3. Ipa Ilana
  4. The Future of COMPAS and Bias in Recidivism Algorithms
  5. Real-World imuse
  6. Awọn ewu & Awọn ọna iṣọ
  7. Ilana Ilana imuse
  8. Tesiwaju Ṣiṣawari
  9. Awọn ibeere ti a beere nigbagbogbo

Akopọ

It became the central case study in algorithmic fairness after a 2016 ProPublica investigation found that its errors fell unevenly by race. The debate that followed showed that common definitions of fairness can mathematically conflict.

Jin Dive

In May 2016, ProPublica published "Machine Bias." It analyzed COMPAS scores for roughly 7,000 people arrested in Broward County, Florida, in 2013 and 2014, and checked who was charged with a new crime within two years. Race is not an input to COMPAS, which uses criminal history and a questionnaire. Even so, ProPublica found that among people who did not reoffend, Black defendants were nearly twice as likely as white defendants to have been labeled higher risk. Among people who did reoffend, white defendants were more often labeled lower risk. Put simply, false positive rates were higher for Black defendants and false negative rates were higher for white defendants. ProPublica also reported that overall accuracy was modest, around 60 percent. Northpointe replied that the tool was fair by a different standard. At each score level, Black and white defendants reoffended at similar rates, so a given score meant the same thing regardless of race. This property is called calibration, or predictive parity. Each side's numbers were largely correct. Researchers then showed why both could be right. Jon Kleinberg, Sendhil Mullainathan and Manish Raghavan, and separately Alexandra Chouldechova, proved that when two groups have different base rates of the outcome, a score cannot be calibrated and also have equal false positive and false negative rates across groups. The only exception is a perfect predictor. So choosing a fairness definition is a value judgment, not a technical detail. In State v. Loomis (2016), the Wisconsin Supreme Court allowed judges to consider COMPAS at sentencing. It ruled that the score could not be the deciding factor and required written cautions to accompany it. A 2018 Dartmouth study by Julia Dressel and Hany Farid found that untrained online volunteers predicted rearrest about as accurately as COMPAS. A common misconception is that leaving race out removes bias. Correlated inputs such as prior arrests can carry historical policing patterns into the score.

Ipa Ilana

Ewu ati ailewu

Ajalu ati awọn ipalara AI lojoojumọ da lori tani o loye awọn ewu ati tani o le ṣe.

Awọn ipinnu diẹ sii

Imọwe ti gbogbo eniyan ati ọjọgbọn ṣe apẹrẹ boya eto imulo aabo to lagbara jẹ iṣe iṣelu ṣee ṣe.

Gige nipasẹ hype

Awọn alaye ti ko o dinku gbigba nipasẹ aruwo, PR lab, ati ile iṣere iṣere aiduro.

The Future of COMPAS and Bias in Recidivism Algorithms

Risk assessment tools are still used in many US pretrial and sentencing settings, and the debate continues. Some reform groups back them as more consistent than unaided judgment, while others argue they entrench historical bias. Likely developments include requirements for local validation, public reporting of error rates by group, and access for defendants to how scores are produced, though the pace varies by jurisdiction. The impossibility result is now a standard part of fairness teaching and shapes audits in hiring, lending and healthcare. It does not settle which definition to use. That remains a policy choice about which errors a society is more willing to accept.

Real-World imuse

In a county that uses COMPAS, a pretrial officer combines a defendant's questionnaire answers with their criminal history. The result is a set of decile scores from 1 to 10 that appears in the report sent to the judge.

After State v. Loomis, a Wisconsin judge who receives a COMPAS report also receives written cautions. They warn that the method is proprietary, that the scores describe groups rather than individuals, and that questions have been raised about racial disparities.

A data scientist auditing a lending model computes both calibration and false positive rates for each group. As with COMPAS, equalizing one breaks the other because the groups' base rates differ.

Researchers following the 2018 Dartmouth study show that a simple model using only age and number of prior convictions predicts rearrest about as accurately as the full COMPAS score.

Awọn ewu & Awọn ọna iṣọ

  • Itoju eewu ayeraye bi sci-fi lakoko awọn agbo ogun agbara.

  • Aabo ọja dada iruju pẹlu titete labẹ adase to gaju.

  • Nlọ kuro ni ti kii ṣe Gẹẹsi ati awọn olugbo ti kii ṣe alamọja pẹlu awọn orisun didara kekere nikan.

Ilana Ilana imuse

  1. Awọn ipalara ọja lọtọ, ilokulo, ati isonu-iṣakoso / awọn eewu aiṣedeede.

  2. Beere ẹri wo ni yoo yi wiwo rẹ pada lori awọn akoko akoko ati idiwo.

  3. Ṣe ayanfẹ awọn orisun akọkọ ati awọn igbelewọn nija lori awọn ẹtọ tita.

  4. Ṣe idanimọ ọna iṣe kan: iṣẹ, eto imulo, igbeowosile, tabi awọn ọgbọn — kii ṣe akiyesi nikan.

Tesiwaju Ṣiṣawari

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Awọn ibeere ti a beere nigbagbogbo

What is COMPAS and Bias in Recidivism Algorithms?

COMPAS (Correctional Offender Management Profiling for Alternative Sanctions) is a commercial risk assessment tool from Northpointe, now Equivant, that scores how likely a defendant is to reoffend. It became the central case study in algorithmic fairness after a 2016 ProPublica investigation found that its errors fell unevenly by race. The debate that followed showed that common definitions of fairness can mathematically conflict.

Among defendants who did NOT reoffend, what did ProPublica find about Black defendants compared with white defendants?

ProPublica found a higher false positive rate for Black defendants. Among people who did not reoffend, Black defendants were nearly twice as likely to have been labeled higher risk.

What was the core of Northpointe's defense of COMPAS?

Northpointe argued predictive parity, also called calibration: a given score corresponds to a similar reoffense rate regardless of race.

Under what condition does the impossibility result say calibration and equal error rates cannot all hold?

Kleinberg, Mullainathan and Raghavan, and separately Chouldechova, showed the conflict arises whenever base rates differ and prediction is imperfect.

What did the Wisconsin Supreme Court hold in State v. Loomis?

The court allowed COMPAS to be used alongside other factors, with written cautions about its limits, but ruled it could not be the deciding factor.

Is race an input to COMPAS?

Race is not an input. Disparities can still arise through correlated inputs and through differences in base rates.