What it means
The risk shows up in several forms. Customer concentration means one buyer accounts for a large share of revenue, supplier concentration means one source provides an input with no ready substitute, and there is also geographic, product and funding concentration, where a single market, line or lender carries too much weight.
It matters because concentration converts a manageable business risk into an existential one. Losing 5% of revenue is a bad quarter, whereas losing a customer worth 40% of revenue usually means redundancies, covenant breaches and, in a leveraged business, a genuine solvency question.
Measurement is usually straightforward: the share of revenue, spend or funding attributable to the largest one, three or five counterparties. Lenders, acquirers and auditors all look at these numbers, and many loan agreements include covenants that trigger if single-customer concentration exceeds an agreed threshold.
The reason concentration persists despite being well understood is that it is commercially rational in the short run. Serving one large account is cheaper than serving fifty small ones, and a single supplier relationship earns better pricing, so the discipline required is to price the risk rather than to pretend it does not exist.
Mitigation is rarely about walking away from good business. The practical responses are diversifying deliberately over time, negotiating longer notice periods and contract terms, qualifying a second supplier even at slightly higher cost, and holding a cash buffer sized to the time it would take to replace the concentrated relationship.
In practice
Real-world examples.
Example
An engineering firm derives 62% of revenue from one aerospace client. Its bank sets a covenant requiring the firm to notify the lender within five working days if that contract is amended, and prices the facility 0.75 percentage points above what a diversified borrower would pay.
Example
A food producer buys a speciality emulsifier from a single plant overseas. When that plant closes for six weeks after a fire, production stops for a month, prompting the company to qualify a second supplier at a 9% higher unit cost as ongoing insurance.
Example
A digital agency notices that 70% of new business arrives through referrals from one partner network. It builds a direct outbound function costing $180,000 a year purely to reduce the channel dependency, treating the spend as risk mitigation rather than growth investment.
Think of it
“Concentration risk is having too many eggs in one basket-overdependence on any single thing.
Formula
Calculation
Customer concentration = (Revenue from the customer / Total revenue) x 100. The same form applies to top-three concentration, supplier spend or any other exposure.
A contract electronics assembler has annual revenue of $8,000,000. Its largest customer accounts for $2,400,000, and its next two largest account for $1,200,000 and $800,000.
Single-customer concentration is ($2,400,000 / $8,000,000) x 100 = 30%. Top-three concentration is ($2,400,000 + $1,200,000 + $800,000) / $8,000,000 x 100 = $4,400,000 / $8,000,000 x 100 = 55%. If the largest customer leaves and the business has a 35% gross margin and $2,000,000 of annual fixed costs, it loses $2,400,000 x 35% = $840,000 of contribution, which turns an $800,000 pre-tax profit into a $40,000 loss unless costs are cut quickly.Case study
Seen in the real world.
Wrenfield Packaging is a fictional carton manufacturer presented here as an illustrative case. For nine years a single supermarket chain provided 58% of its revenue, and the relationship was cited internally as evidence of quality rather than as an exposure.
When the supermarket consolidated its supplier list, Wrenfield was given six months' notice. Revenue fell from $14,000,000 to about $5,900,000 within a year, and because roughly $3,800,000 of costs were fixed factory overheads, the fictional company moved from a $1,100,000 profit to a substantial loss before it could close one of its two sites.
The illustrative lesson its rebuilt management team drew was to set a hard internal rule: no customer above 25% of revenue, with any account approaching that limit triggering a formal diversification plan and a required cash reserve equal to six months of that account's contribution. The rule cost Wrenfield some volume, and it also meant the next customer loss was survivable.
Watch out
Common mistakes.
- Measuring concentration by revenue only, when a customer at 20% of revenue but 45% of gross profit is the more dangerous exposure.
- Overlooking hidden concentration, such as five separate customers who all belong to the same parent group or all serve the same end market.
- Treating a long-standing relationship as low risk because it has never failed, which confuses history with contractual protection.
Questions
People also ask.
What level of customer concentration is acceptable?
There is no universal limit, but many lenders and buyers become cautious above 20% to 25% from a single customer, and above 50% from the top three.
Does a long contract remove concentration risk?
It reduces the timing risk by giving notice, but it does not remove the exposure, since counterparties can fail, renegotiate or simply decline to renew.
How does concentration risk affect a business sale?
It usually lowers the valuation multiple, because a buyer prices in the chance of losing the key relationship shortly after the transaction completes.
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