How to Simulate a Loan Portfolio Using Behaviour (Roll Rates)
This is not a textbook explanation. This is how I actually think about portfolios when someone asks: “What will my book look like after 6 months?” “Why are my NPAs rising even though disbursements are stable?” “What happens if my collection efficiency drops slightly?” Let’s start from first principles and build our way up. Step 1: The easy part. Total AUM forecasting If all you care about is overall AUM , life is simple. You take: Opening AUM Add fresh disbursements Subtract normal amortisation Subtract prepayments And you get closing AUM. For example: Particulars Amount (₹ Cr) Opening AUM 100 Disbursements +20 Normal amortisation −8 Prepayments −2 Closing AUM 110 This works fine if you don’t care where the AUM is sitting . But lending is never that simple. Step 2: Why bucket-wise AUM actually matters Most real decisions depend on where the AUM sits, not just how much. Bucket-wise AUM is required for: ECL provisioning Understanding delinquency buil...