The title is both a statement and a question, and in the talk you will find
a list of things that are wrong with the chain ladder technique but also a
question asking whether it is so bad after all! In fact, the chain ladder
technique has a lot going for it - it is simple, it is widely used and it is
pretty well understood. However, it has some significant faults: for example,
the fact that it does not include any calendar year effects. More
fundamentally, it is just a technique (an algorithm) for filling in the rest of
a rectangle when you just have data in the upper left corner. It doesn't use
any risk theory; it doesn't make any assumptions about the way the data have
been generated; and the parameters amalgamate changes that are due to a variety
of different sources. In all other areas of actuarial science, it is usual to
consider the mechanisms generating the data and build models using these
fundamental principles. For example, in rating it is common to use data on
claims frequency and claims severity and then consider carefully what the
results tell you before deciding how to set next year's premiums.
In the talk, I explain how it is possible to consider reserving models from
first principles as well, and yet retain the appealing simplicity of the chain
ladder technique. Using just one extra triangle, it is possible to separate out
the payment delay from the reporting delay. This might be very important
because it is quite possible for these to have different characteristics over
time. So, just like in premium rating, it is possible to make informed
decisions about the likely future properties of these delays, and thereby set
reasonable (and justifiable) assumptions for any solvency and capital models.
Instead of using an ad hoc method, and making ad hoc adjustments, it is
possible to use an approach which uses real quantities which have a physical
interpretation.
There are 3 papers associated with this talk. The first two ("Prediction of
RBNS and IBNR claims using claim amounts and claim counts" and "Cash flow
simulation for a model of outstanding liabilities based on claim amounts and
claim numbers") describe the basic model which is used as an alternative to the
chain ladder technique. The third paper ("Double Chain Ladder") is an extension
of the basic model, and is very closely related to the standard chain ladder
model. In fact, it shows that (if certain choices are made about the model and
the estimation) it is possible to get exactly the same results as the standard
chain ladder model. It could be argued therefore, that this model is an
alternative stochastic model for the chain ladder model.
The new models have some further advantages. For example, they separate out
the RBNS and the IBNR reserves, and they produce a tail, beyond the latest
development year, without having to make any further assumptions.