Digital twin-enhanced credit risk prioritization in mortgage portfolios: a hybrid model approach
摘要
The growing level of household indebtedness amid macroeconomic instability increases the need for tools for early diagnosis of mortgage portfolio credit risk. Despite the widespread use of probability of default (PD) models, their limited sensitivity to borrower behaviour and digital characteristics reduces the effectiveness of targeted risk mitigation. This creates a research gap in terms of integrating digital indicators into credit ranking at the borrower and portfolio segment levels. The aim of this study is to develop and empirically test a hybrid composite model (HPCS) that combines traditional risk parameters (PD, LGD, EAD) and digital behavioural indices of the borrower (TRI, ARI) within the concept of a digital twin. The methodological basis includes weight calculation using the CRITIC method, robust normalisation, and empirical testing on a sample of 1,000,000 mortgage loans based on Fannie Mae data for 2022–2024. To assess the model’s effectiveness, we propose the EL-capture metric, which reflects the share of expected losses covered in the portfolio at a given level of intervention. The results show that with 10% coverage, the HPCS model covers 3.8 percentage points more expected losses than the PD model. The HPCS and EL heat maps demonstrate spatial consistency across high-risk segments in the LTV