提出横向搜索框架,帮机构在资源有限时选出更公平的贷款模型。
Selecting for Less Discriminatory Algorithms: A Relational Search Framework for Navigating Fairness-Accuracy Trade-offs in Practice
- 通过跨模型族横向搜索,寻找公平性更优的算法组合。
- 基于2021年HMDA数据验证,在真实信贷场景中实现可落地的公平性优化。
- 适合政策执行、金融监管等需平衡公平与效率的实践场景。
随着机器学习模型在高风险决策中广泛应用,如何为特定任务、受众和行业选择合适算法成为关键挑战,尤其在公平性维度。传统公平性评估常将公平性视为理想条件下的数学属性,将模型选择简化为优化问题,却忽视了模型多样性——多个模型可具备相似性能但不同公平特征。法律学者提出的“较不歧视算法”(Less Discriminatory Algorithms, LDAs)将模型选择视为民事权利义务。但在实际部署中,公平性实验受限于监管标准、机构优先级和资源能力。本文基于更新的2021年房屋抵押贷款披露法案(HMDA)数据,重新审视李与弗洛里迪(2021)提出的关联公平性方法,拓展LDAs搜索范围。我们主张水平扩展LDAs搜索,考察不同模型族间的公平性差异,可在非实验性、资源受限环境下,作为超参数调优的轻量级补充或替代方案。仅依赖公平性指标不足以准确评估候选LDAs;通过结合横向搜索与关联权衡框架,我们在真实信贷结果上展示了负责任的最小可行LDAs搜索。组织可据此系统比较、评估并选择在特定领域上下文中兼顾公平与准确的最优算法。
原文摘要 · Abstract (English)
As machine learning models are increasingly embedded into society through high-stakes decision-making, selecting the right algorithm for a given task, audience, and sector presents a critical challenge, particularly in the context of fairness. Traditional assessments of model fairness have often framed fairness as an objective mathematical property, treating model selection as an optimization problem under idealized informational conditions. This overlooks model multiplicity as a consideration--that multiple models can deliver similar performance while exhibiting different fairness characteristics. Legal scholars have engaged this challenge through the concept of Less Discriminatory Algorithms (LDAs), which frames model selection as a civil rights obligation. In real-world deployment, this normative challenge is bounded by constraints on fairness experimentation, e.g., regulatory standards, institutional priorities, and resource capacity. Against these considerations, the paper revisits Lee and Floridi (2021)'s relational fairness approach using updated 2021 Home Mortgage Disclosure Act (HMDA) data, and proposes an expansion of the scope of the LDA search process. We argue that extending the LDA search horizontally, considering fairness across model families themselves, provides a lightweight complement, or alternative, to within-model hyperparameter optimization, when operationalizing fairness in non-experimental, resource constrained settings. Fairness metrics alone offer useful, but insufficient signals to accurately evaluate candidate LDAs. Rather, by using a horizontal LDA search approach with the relational trade-off framework, we demonstrate a responsible minimum viable LDA search on real-world lending outcomes. Organizations can modify this approach to systematically compare, evaluate, and select LDAs that optimize fairness and accuracy in a sector-based contextualized manner.
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