How DO they work?

Do they apply a standard multiplier (given the driver's history, postcode etc, if grp 4 times by x, if grp 6 times by y etc)?

Does it depend on whether third party or comp?

Are the calculations in the public domain, i.e is there a website where we could find out that e.g. all other things being equal grp 6 = grp 4 x 1.5, grp 19 = grp 6 x squillions etc?

Or if not exact percentages are there any general rules of thumb?

Would be surprised if you could find any of the algorithms in the public domain - they are very complex and based upon many factors, and some people get paid a fair amount of cash to come up with them...

General rule of thumb...the higher the group rating for the car, the higher the insurance. However, different cars will get different quotes irrespective of insurance grouping...

Rob.

Yeah, when it comes to insurance you should always shop around. Insurance companies have a specific type of motorist that they are looking to insure. Thats why quotes vary so much. If its a high quote then chances are they don't really want your business as they think your a bad risk. If its low, you match the criteria they're looking for in a policy holder.