Years and percentages are great for advertising but can be close to meaningless.
On the right there is a table of the number of years NCD and the percentage discount that the years represent for three of the quoters.
The first noticeable fact is that the three schemes all have a point where more years NCD does not result in a greater No Claims Discount, and that this point is at a different number of years.
The Alcohol Recovery scheme is cautious with how it allows NCD, it is trying to address the issue of does the driver still drink and drive and if so is he just getting away with it and another incident is likely?
There are big jumps in the discount after 1 and 3 years claim free, the rationale being a year drink free and then allow time for a relapse and the subsequent incident.
The Young Driver scheme hits the maximum NCD after only three years, this is simply because the driver ceases to be a young driver at this point and needs to be moved onto other schemes.
The Mainstream quoter actually has negative NCD, drivers with no NCD get a 10% loading, as the scheme is aimed at the normal safe driver why would that driver not have any NCD?
Possibly because of claims, possibly because of a lack of recent driving experience as the main driver of a vehicle.
Again because it is a safe driver scheme the maximum NCD percentage is quite low and after 4 years NCD doesn't increase by the much.
The point is that NCD years and percentages can easily become a marketing tool, and a 75% NCD from one scheme may stil result in higher premium than a 40% NCD from another scheme.