Scorecard Và PD Band: Biến Model Score Thành Ngôn Ngữ Policy

Điểm cần nhớ

• Model score không tự nói được policy; PD band mới giúp Risk và Business ra quyết định.
• Scorecard vẫn sống khỏe trong credit risk vì explainability, auditability và reason code.
• WOE/IV hữu ích để đọc feature, nhưng IV quá cao là tín hiệu phải kiểm tra leakage.
• Actual bad rate by band kiểm tra risk ordering; predicted PD vs actual bad rate kiểm tra calibration.
• Cum bad rate cho thấy portfolio tại cutoff; marginal/bin bad rate cho thấy nhóm approve thêm rủi ro thế nào.

A model score needs policy language

A model score is not the final language of credit decisioning. It has to become approval bands, limit rules, pricing tiers, manual review queues and monitoring guardrails.

Why scorecards still matter

Scorecards remain useful because they are explainable, auditable and easy to operationalize. ML models may rank better, but they still need to be translated into PD bands and decision rules.

Band monitoring

Monitor volume, average predicted PD, actual bad rate, cum rate, cum bad rate and marginal/bin bad rate. Actual bad rate by band checks risk ordering. Predicted PD versus actual bad rate checks calibration.

Practical takeaway

If PD <= 7.5% gives a cumulative bad rate below risk appetite, do not stop there. Check the marginal group 5% < PD <= 7.5%. That is the group your new policy is actually adding.