Besides the qualitative reasons, there are also some quantitative causes.
For instance, a loss occurred in the first quarter and the amount was estimated at £50K initially. In the second quarter the amount was re-estimated at £80K, and in the third quarter it developed to £100K. So the quarter-to-quarter loss development factors were 1.6 and 1.25.
If there was a deductible of £20K, then the quarterly loss amount would be £30K, £60K and £80K. As well, the quarter-to-quarter loss development factors were 2.0 and 1.333.
If the deductible was £40K rather than £20K, then the quarterly loss amount would be £10K, £40K and £60K. Meanwhile, the quarter-to-quarter loss development factors were 4.0 and 1.5, correspondingly.
So you can see what happened to the development factors.