Net Interest Margin Compression
Net Interest Margin (NIM) compression occurs when the cost of a bank's liabilities — primarily deposits — rises faster than the yield on its loan book, squeezing the spread between what the bank earns on advances and what it pays depositors.
Net Interest Margin is one of the most closely watched profitability metrics for Indian banks. It is calculated as net interest income divided by average earning assets. When deposit rates rise — driven by RBI policy tightening, competitive pressures, or a shift in depositor preference toward term deposits from low-cost CASA — but lending rates cannot be repriced upward at the same pace, NIM compresses.
The transmission asymmetry is structural. On the liability side, banks must reprice deposits as existing fixed-rate term deposits mature and depositors demand higher rates in a rising rate environment. On the asset side, a large portion of the loan book may be fixed-rate, or repricing may be delayed by the MCLR reset cycle — which is typically one year for most loans. External benchmark-linked loans (EBLR) reprice immediately when the policy rate changes, which cuts both ways: helping banks during rate hikes but causing faster NIM compression when rates fall.
The RBI rate hike cycle of 2022-23, which raised the repo rate by 250 basis points, initially widened NIMs for banks with floating-rate loan books that repriced quickly. However, as deposit rates caught up through 2023, many mid-sized private and public sector banks reported NIM compression of 10-20 basis points in FY24. The CASA ratio became a key determinant of resilience — banks with high current account and savings account balances (which carry near-zero or regulatory-floor interest costs) were better insulated.
Competition from government small savings schemes — which offer politically sticky higher rates — and mutual fund liquid and overnight funds further eroded the low-cost deposit franchise. During periods of tight liquidity in the banking system, banks aggressively competed for term deposits, pushing bulk deposit rates to 8-9% for some maturities, further squeezing margins.
For equity analysts, NIM trajectory is a leading indicator of bank profitability. A sustained 10-basis-point compression on a loan book of Rs 10 lakh crore translates to roughly Rs 1,000 crore in lost annual net interest income. Banks counter NIM pressure by growing fee income, optimising their asset mix toward higher-yielding segments like retail and MSME, and managing the liability mix actively. Monitoring quarterly NIM disclosures alongside the CASA ratio and loan repricing schedules is essential for understanding forward earnings trajectories.