Loss Ratio Method
The loss ratio method builds an overall rate indication by comparing projected loss needs and fixed expenses against the premium that remains available after variable expenses and profit provisions.
- Role
- Concept
- Level
- Core
- Time
- Reference
- Freshness
- Stable
Plain-English Definition
The loss ratio method starts from premium rather than cost per exposure. It asks a simple question: given projected losses, fixed expenses, variable expenses, and profit needs, is the current premium level high enough?
That makes it a useful companion to the pure premium method. Pure premium thinks in cost per exposure. Loss ratio thinks in premium adequacy and the share of premium that can actually be spent on losses.
Worked Example
Suppose the projected loss and LAE ratio is 68%, fixed expenses are 7% of premium, variable expenses are 22%, and the profit-and-contingency provision is 5%. The permissible loss ratio is 1 - 0.22 - 0.05 = 0.73.
The numerator of the indication is 0.68 + 0.07 = 0.75. The indicated change factor is 0.75 / 0.73 = 1.0274, so the method points to about a 2.7% overall increase.
That result means current rates are close to adequate, but slightly low, given the projected loss need and the expense structure built into the indication.
Why Actuaries Use It
Exam 5 includes the loss ratio method because it is a standard overall-rate-indication tool. It fits naturally when premium data is already central to the analysis and when the pricing conversation is framed in terms of premium adequacy rather than only cost per exposure.
In practice, actuaries often compare the loss ratio method against the pure premium method. If both point in roughly the same direction, confidence usually goes up. If they diverge, the data treatment or assumptions need another look.
Common Mistakes
A common mistake is using premium that has not been adjusted to the current rate level. If premiums are not on-leveled first, the loss ratio indication can be distorted before the actual ratemaking logic even begins.
Another mistake is mixing fixed-expense treatment and variable-expense treatment without being explicit about the denominator. The method is straightforward only when each provision is being handled consistently.
Connection To Exam 5
The current outline explicitly includes constructing overall rate level indications using both the pure premium and loss ratio methods. That makes this one of the core ratemaking pages in the CAS cluster rather than a side note.
It also sits naturally beside on-leveling and trend, because the loss ratio method only says something useful if premium and loss inputs have already been adjusted onto a comparable basis.