What is deposit concentration risk for banks?

The short answer

Deposit concentration has three distinct dimensions, often confused. The first is size concentration: a few accounts holding a disproportionate share of liabilities. The second is sectoral concentration: depositors from a single industry whose financial health rises and falls together. The third is structural concentration: a high share of uninsured balances, which lack the FDIC anchor that stabilizes retail deposits.

Banks routinely live with size concentration — corporate banking is built on it. The fragility emerges when size, sector, and uninsured status combine. A bank with 100 large clients in different industries is less fragile than a bank with 10,000 small clients in the same industry, even if average account size suggests the opposite.

Correlated behavior is the underlying driver. Depositors who share information sources, professional networks, or industry stress signals tend to withdraw together.

→ New to bank funding structures? Systemic fragilities pillar

What the data shows

Concentration ratios at failed banks (FDIC, regulatory filings, 2023):

• SVB: 86.4% of $175bn deposits were uninsured at year-end 2022. The top 10 accounts held $13.3bn collectively. Average account size above the FDIC limit exceeded $4 million
• Signature Bank: large exposure to crypto-related deposits, with reporting suggesting 90%+ uninsured at the depositor level for many accounts
• First Republic: ~67% uninsured deposits before its collapse in May 2023, with concentration in high-net-worth West Coast clients
• Comparison baseline: median uninsured deposit ratio at large US banks was around 50% in 2022, with significant dispersion across institutions

The exception that nuances the pattern: large universal banks with diversified client bases — JPMorgan, Bank of America — also have high absolute uninsured balances but display lower correlation in withdrawal behavior across sectors and geographies. The risk is concentration, not absolute scale.

→ Dataset: Bank lending standards

Why it happens — the macro mechanism

Deposit concentration interacts with bank fragility through three reinforcing channels.

The behavioral correlation channel. Depositors who share an information environment update their beliefs in unison. Tech founders connected through venture capital networks, crypto firms reading the same Discord channels, or community banks serving the same regional industry all face this. When one depositor signals concern, the rest follow within hours rather than weeks.

The size-and-mobility channel. Large uninsured deposits are managed by treasurers with the operational capacity to move funds in minutes via wire transfer. Contrary to the textbook framing where deposit stability scales with size — based on relationship banking arguments — the digital era has reversed this: the largest accounts are the most mobile and the most likely to act on early signals. This is the angle that traditional banking risk frameworks did not capture.

Bridging point: the regulatory framework also amplifies concentration risk through its design choices.

The regulatory threshold channel. Banks below $250bn in assets faced lighter supervision under the EGRRCPA changes of 2018, including reduced stress testing and weaker liquidity rules. Bank stress tests details how this gap left mid-sized concentrated banks under-monitored relative to their actual fragility.

Synthesis by regime: in pre-FDIC banking (1873-1933), concentration was geographic — local banks served local economies, and a regional shock cascaded through correlated withdrawals. Under post-FDIC universal banks (1934-2007), concentration shifted to sectoral specialization at smaller institutions, but deposit insurance limited the run dynamic. In the post-2007 regime, deposit insurance ceiling stagnation combined with industry specialization to recreate fragility — SVB’s 86.4% uninsured ratio in a single-sector clientele was the extreme expression.

The most dangerous deposit concentration is not the size of accounts but the correlation of behavior — homogeneous clients withdraw together.

→ Framework: Systemic fragilities

What it means for different economic actors

Bank shareholders. Concentration ratios should be a primary screening criterion alongside capital ratios. The 2023 episode demonstrated that two banks with identical CET1 ratios can have very different run probabilities depending on uninsured share and client homogeneity.

Corporate treasurers. Diversifying operating accounts across multiple banks reduces the firm’s exposure to any single bank’s failure — but also reduces concentration at the system level. The standard threshold is to keep balances within insured limits where possible and split larger amounts across institutions or sweep into Treasury bills.

Regulators. Post-2023 supervisory thinking shifted toward incorporating uninsured deposit ratios and depositor-base homogeneity into the stress-test framework. Earlier rules focused on aggregate liquidity coverage rather than the correlation structure of withdrawal behavior.

A common error is to treat large diversified banks as inherently more risky than small specialized ones because of their absolute size. Correlation, not size, is what determines run dynamics.

Practical observation

Go deeper

Related questions

• Why did SVB fail so quickly in March 2023?
• What causes a bank run and why are they self-fulfilling?
• How does FDIC insurance actually work?
• How does social media accelerate bank runs?

Frequently asked questions

Is deposit concentration always a risk indicator?

It depends on the type. Size concentration in a diversified client base — a corporate banking division with large multinational clients across industries — is manageable through standard liquidity tools. Sectoral concentration with high uninsured share is structurally fragile because it combines correlated behavior with weak insurance anchoring. The same headline number can mean very different things depending on the underlying composition.

How does this differ from credit concentration?

Credit concentration refers to a bank’s loan exposure being concentrated in one borrower, sector, or geography — the asset side. Deposit concentration is on the funding side. Both can produce systemic events but through different mechanisms: credit concentration crystallizes through defaults over months or years, while deposit concentration crystallizes through withdrawals over hours or days. The 2023 episode was driven primarily by deposit-side concentration.

What is the angle distinctive of behavioral correlation?

Standard concentration metrics — Herfindahl indices, top-10 client share — measure size distribution but not behavioral correlation. Two banks with identical Herfindahl scores can face very different run risks if one serves a homogeneous tech clientele connected through VC networks while the other serves diverse small businesses across regions. The behavioral dimension is harder to measure but ultimately more relevant — this is the lesson of 2023 that traditional risk frameworks are still incorporating.

Last updated — 1 June 2026