Ceri JC

When pressed for that, they always hide behind, "Well, we can't show that, because otherwise people would work out what to say to get lower premiums." For example, one of the insurers is now looking at previously unasked things, such as where you get your bike serviced, to make the quote more accurate, but won't give away the specifics for fear of people manipulating it to get lower quotes.

I don't buy into that defense/reasoning at all; People have been well aware of the fact for years, that garaging your bike lowers the premiums, yet by and large, people don't lie about it. This is because they know full well if the bike is nicked and they come and look and say, "you haven't got a garage", the claim is invalid. This is exactly the same; if people lied to lower their premium, based on seeing the risk calculation maths, they'd be similarly be left out to dry in the event of a claim when they were found out.

So, that leaves one plausible explanation; the maths behind their calculations is so flawed that they would get drawn into lengthy discussions with and customer with even a rudimentary understanding of probability.