What it means
An insurer buys reinsurance to transfer an agreed portion of risk. In excess-of-loss cover, the reinsurer responds above an attachment point up to a limit.
Rate on line relates the premium to that limit, not to every possible loss the insurer might face. Suppose a layer provides $20 million of cover above a $10 million retention.
A $2 million premium produces a ten percent rate on line. The denominator is the $20 million layer, not the $30 million point at which that layer ends.
Two layers can have equal limits and equal rates while covering very different loss ranges, since protection beginning after a small loss may respond much more frequently than protection attaching only after an extreme event. An unchanged rate on line can also hide a price improvement when the retention falls, because the ratio stays the same while the buyer obtains protection that responds sooner.
Compare the risk transferred as well as the premium per unit of nominal limit. Rate on line also does not equal expected claims divided by premium.
Reinsurers price for loss frequency and severity, expenses, capital and other considerations. The quoted premium-to-limit ratio alone cannot tell a manager whether the seller will earn a profit or the buyer is overpaying.
Contract terms complicate comparisons further. A reinstatement can restore exhausted coverage, potentially for an additional premium, so a base rate calculated before that extra premium may not describe the buyer's eventual cost or the total protection available under the full treaty.
A simple reciprocal is sometimes called a payback period: at a twenty percent rate, limit divided by annual premium is five, but that arithmetic is not a forecast that the reinsurer will repay claims in five years, nor a guarantee that the insurer will recover its premiums. For a business manager reviewing insurance costs, ask what limit and premium are used, what losses trigger the layer and what additional payments may apply.
Keep currency, coverage period and scope consistent.
In practice
Real-world examples.
Example
A fictional insurer compares $1 million of premium for $10 million of cover with $2 million for $20 million. Both have a ten percent rate on line.
Example
A fictional renewal keeps the premium and limit unchanged but raises the retention. Its rate on line is unchanged, although the insurer now absorbs more loss before the layer responds. Reporting this as an unchanged bargain hides a meaningful reduction in protection.
Example
A fictional treaty restores a used layer after a covered event for an extra payment. The buyer calculates the base rate on line, then separately models the reinstatement premium. The simple opening ratio should not be presented as the complete cost in every claim scenario.
Formula
Calculation
Rate on line = reinsurance premium / coverage limit x 100 percent.
For a fictional $4 million premium and $20 million limit, rate on line = $4 million / $20 million x 100 = 20 percent. A simplified reciprocal, $20 million / $4 million, is five annual premium amounts.
That reciprocal assumes the same annual premium for comparison purposes. It ignores expenses, investment income, actual claims, contract renewal changes and additional premiums. Use the stated layer limit rather than the retention plus limit, and identify whether the quoted premium includes applicable extras.Case study
Seen in the real world.
In this fictional case, Harbor Property Insurance reviews a catastrophe layer priced at $3 million for $30 million of cover. Its ten percent rate on line matches the prior year's ratio. The purchasing summary initially calls the renewal unchanged. Risk staff notice that the new attachment point is higher. Harbor would retain more of a medium-sized catastrophe before reinsurance starts paying.
The team also checks a reinstatement provision, because another event could create an additional premium payment. Harbor separates the ratio from its coverage assessment. It shows the board the premium, layer limit, attachment point and modelled retained losses under each option. The exercise does not prove either offer is correctly priced, but prevents a stable headline percentage from being mistaken for stable risk transfer.
Watch out
Common mistakes.
- Dividing premium by retention plus limit rather than the stated amount of cover in the layer.
- Ranking treaties by rate on line without comparing attachment points, coverage scope and reinstatement terms.
- Calling the ratio a probability, profit margin or guaranteed payback period when it is a premium-to-limit measure.
Questions
People also ask.
Is a lower rate on line always preferable?
No. It can reflect coverage that responds less often or different terms. Compare the actual risk transferred.
Does ten percent mean a ten percent chance of a claim?
No. Rate on line is premium divided by cover. It is not a direct estimate of claim probability.
Is rate on line the same as a loss ratio?
No. A loss ratio compares claims with premium, while rate on line compares premium with the amount of cover.
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