Negative policy rates compress the spread between what banks earn on assets and what they pay for liabilities, directly affecting Net Interest Margin. When central banks set policy rates below zero, short-term market rates fall and banks face two linked pressures: the yields on loans and securities decline, and deposit rates cannot fall below a certain floor without provoking withdrawals or reputational damage. Claudio Borio Bank for International Settlements explains that prolonged low or negative rates tighten margins by reducing the return on new loans faster than deposit costs adjust, especially when deposit pass-through is limited. That mechanism is a core channel through which monetary policy influences bank profitability.
Transmission and bank business models
The immediate cause is asymmetric pass-through: loan rates tend to follow policy down, but deposit rates hit effective lower bounds because households and businesses resist nominal negative balances. Consequently, banks funded largely by deposits see compressed interest income. Hyun Song Shin Bank for International Settlements emphasizes that banks with low fee income and heavy reliance on retail deposits are most exposed. Wholesale-funded banks or those with diversified non-interest income can partly offset this effect, at the cost of different risks.
Broader consequences and behavioral responses
Compressed net interest margins can prompt banks to seek compensation by charging higher fees, lengthening loan maturities, increasing risk-taking, or shifting toward non-interest-bearing services. European Central Bank staff analysis documents banks increasing fee-based activities and altering asset mixes to protect earnings. For communities with strong saving cultures, such as parts of northern Europe or Japan, cultural reluctance to accept negative deposit rates forces banks to accept smaller margins rather than pass costs to depositors, with tangible consequences for profitability in regional banks and credit availability in rural territories. Smaller banks often lack scale to replace lost interest income with fees or trading gains.
Environmental and systemic dimensions arise when margin pressure encourages riskier lending to maintain return on equity, potentially weakening credit quality and concentrating risk in housing or commercial real estate sectors. Regulators therefore monitor capital buffers and liquidity profiles to ensure that margin compression does not translate into reduced lending or financial instability.
In sum, negative policy rates lower Net Interest Margin primarily by compressing the spread between asset yields and deposit costs; the size of the effect depends on funding structure, market competition, and client behavior. Evidence from central bank researchers and international institutions shows banks adapt in diverse ways, with consequences for profitability, risk-taking, and regional credit provision. Policy designers weigh these trade-offs against macroeconomic objectives when considering negative rates.