Carrier concentration is the risk that doesn't show until the carrier leaves, and the 30-55 rule is the bright-line screen buyers use to flag it early. It's two simple tests, but the thresholds aren't arbitrary — they mark the points where concentration stops being a manageable feature and becomes a structural threat to the combined book. A buyer applies the rule as a fast first pass, then uses the result to decide whether the target moves through diligence smoothly or triggers the deeper scrutiny.
§ 01 · The two-part ruleTwo tests, one portfolio.
| Test | Threshold |
|---|---|
| Single-carrier cap | No single carrier above 30% of revenue |
| Top-3 cap | Top three carriers combined below 55% |
The rule is two independent tests applied to the same portfolio: no single carrier above 30% of revenue, and the top three carriers combined below 55%. Both have to pass — an agency can clear the single-carrier test while failing the top-3 test (three carriers at 20% each is 60%), or vice versa. A passing profile — a top-1 in the low 20s and a top-3 in the 40s — produces a clean diligence profile, a faster process, and premium multiples, with the valuation uplift typically exceeding the seller's expectations. The two-part structure is what makes it a real screen rather than a single ratio, and the same threshold from the carrier-diligence side is covered in the carrier-DD 30-55 rule.
§ 02 · Why 30 and 55The threshold rationale.
The thresholds mark real inflection points. 30% is where a carrier loss turns from manageable to catastrophic — losing 15% can be re-placed across 12–18 months, but losing 35% delivers a structural revenue shock that takes multiple years to recover, if ever. 55% is where diversification stops providing meaningful protection — above it, the agency has effectively become a 3-carrier shop with a ceremonial long tail.
The numbers aren't round-number conventions; they mark where the risk changes character. Below 30%, the loss of a carrier is a recoverable event — the agency re-places the book across its other appointments over 12–18 months. At 30%+, the same loss becomes a structural revenue shock that takes years to recover or never fully does, which is why 30% is the line where a carrier relationship shifts from an asset to a single point of failure. The 55% top-3 cap addresses the portfolio-level version: above it, the long tail of small appointments is ceremonial — the agency is functionally dependent on three carriers, and adding a tenth small appointment doesn't change that. A buyer who internalizes the why behind the thresholds reads a near-miss (32% versus 29%) correctly: operationally similar, but a disciplined buyer still uses the bright line as a consistent screen.
§ 03 · When it failsThree restructures and the rebalance.
Failing the rule doesn't kill a deal — it triggers one of three structural adjustments, scaled to severity. An earnout or holdback tied to the specific concentration risk (for example, 85% at close plus 15% over 2–3 years conditional on the concentrated appointment's retention) shares the risk until it resolves. A valuation multiple discount — a half-turn to a full-turn of EBITDA for a seriously over-concentrated book — prices the risk directly. And a walk-away applies when the concentration is severe enough that a transition failure would reshape the buyer's own economics. For a seller, the rule is also a pre-market to-do: concentration drifts upward by default in unmanaged books (new production gravitates to the carriers the agency places most), but an agency at 34% single-carrier can often reach 27%–28% inside 18–24 months through deliberate placement steering — directing new production and selective remarketings to the next 2–3 carriers in the portfolio without sacrificing existing relationships. The same logic rebalances a 62% top-3 below 55% if carriers four through seven have headroom.
§ 04 · Three scrutiny questionsWhat "fail" actually triggers.
When the rule fails, it triggers three diligence questions rather than a reflexive discount — because not every over-concentration carries the same risk. First, transferability of the concentrated appointment: review the change-of-control provisions to learn whether the appointment is unambiguously transferable or requires carrier consent that hasn't been pre-verified, which is the difference between a manageable concentration and a deal-breaking one. Second, the quality and stability of the concentrated relationship: a 20-year named-principal relationship is far more durable than a 3-year field-rep-dependent one, even at the same percentage. Third, the realistic remediation counterfactual: if the concentrated carrier exited tomorrow, what share of the book could be re-placed with the target's existing appointment set? Those three answers determine whether a failed screen warrants an earnout, a discount, or a walk. The rule, in the end, is a screen, not a diagnostic — passing earns normal diligence treatment, failing earns the three questions, and the change-of-control provisions that decide transferability are in change-of-control provisions.
◆
Terminology on this shelf
- The 30-55 rule
- Two tests — no single carrier above 30%, top-3 combined below 55%.
- The 30% line
- Where a carrier loss turns from manageable (re-placeable in 12–18 months) to catastrophic.
- The 55% line
- Where diversification stops protecting — a 3-carrier shop with a ceremonial tail.
- Three restructures
- An earnout/holdback, a half-to-full-turn EBITDA discount, or a walk-away.
- Rebalancing window
- 18–24 months of placement steering can move a 34% single-carrier to 27%–28%.
- Screen, not diagnostic
- Failing triggers three scrutiny questions — transferability, quality, remediation — not disqualification.