One of the problems with a run-off triangle is that there is very little data at the tail (ie in the final column). For example, if a run-off triangle is used in the previous example then the claims data from origin years 2003–2007 is ignored. In the section about run-off triangles, what does the above sentence mean?
If you use a triangle in the strictest sense of the word then in the last (right-hand most) column there will be one entry (ie in the top row). So you will therefore exclude data in prior years to your most recent fully developed year. The diagrams on page 6 explain this.
