For the life of me, I cannot see the logic of allowing discrimination on age grounds which simultanously excludes discrimination on gender which is evidence-based. Both are equally imperfect disciminations; there will be reckless older drivers as much as there are careful young males. The basis for these differentials is averages, and surely this applies to all ways in which insurers set premiums.
I agree that in most instances the age grounds are purely statistical and not because of the age
per se. Thus 40 year olds are better drivers than 20 year olds but not because of their age but because of, say, their driving experience, their attitudes etc. If society was concerned about age discrimination in motor rates then it would ban age rating and force companies to go directly to the causes. But society does not currently regard age rating in this area as offensive.
But using race as a rating factor is unacceptable to the majority in our society.
A priori it is surely highly unlikely that people of different race who display quite marked biological differences otherwise would be exactly equal when it comes to biological longevity. Yet I think race differentiation in insurance pricing is banned.
Or take religion for that matter. I am quite sure that there are differences in risks which show some religious correlation, especially in societies like NI were religion would correlate to other social differences. Indeed religion may even be a direct risk factor, for example if it precludes one taking blood transfusions.
We have got used to gender rating in insurance and therefore tend to not regard it as offensive. Once this ruling gets bedded in I foresee a situation in 20 years time when people will marvel in disbelief how at one time young males were charged twice young females just as today we think how strange that at one time we could smoke in cinemas.
Finally, if society places a higher value on equality than on accurate insurance pricing, even if that differential pricing is directly justified (as opposed to statistically supportable), then it is open to society to force this equality on the markets whilst still preserving stable competition. One route is Risk Equalisation which is how we are going to address health insurance, where clearly age is a direct risk factor.