Calculating Insurance premiums

[Devonian]

Anybody have any idea how our beloved insurance companies calculate their premiums. I always thought they used a kind of scoring system giving and taking away points for positves and negatives, age geographic location claims history etc. Yet if you go on say confused.com and type in all the details you get specific quotes. Duplicate this say a week form now and you can get wildly different quotes. For example. My son insured his first car a few months ago being 17 and with no no-claims bonus we expected to pay quite a bit, just over £1000 in fact. Now 3 months later inputting exactly the same data for the same car the best quote we can get is over £1500
Similarly adding my son to my car policy changes the £300 premium to over £3,000 whereas insuring the same car in my wife's name (same age and claim history) with my son as additional driver costs £1,000 less.
Does anyone know how they calculate their premuims?

 

[Rory]

whereas insuring the same car in my wife's name (same age and claim history)

What, your wife's 17?

I think it's a lot to do with gender - we added our daughters as soon as they were 17 onto wife's Clio 1.6 (group 6) and it went up a couple of hundred pounds.
They both got their own insurance at 21 on new group 3 cars and that cost around £500 fully comp, with Admiral. Adding an older additional driver usually reduces the premium for younger drivers.

 

[Devonian]

What, your wife's 17?

I think it's a lot to do with gender - we added our daughters as soon as they were 17 onto wife's Clio 1.6 (group 6) and it went up a couple of hundred pounds.
They both got their own insurance at 21 on new group 3 cars and that cost around £500 fully comp, with Admiral. Adding an older additional driver usually reduces the premium for younger drivers.

Umm yes it does read a bit like that doesn't it -- what i meant of course is she is the same age as me -- which is slightly more than 17 lol