insurance is a risk based investment proposition, it always has been and will never not be such. an increase in membership numbers increases risk, (which it would with higher membership numbers) premiums would go up because the potential to pay claim losses goes up (it is impossible to increase risk potential and have the risk go down),......it simply does not and cannot work any other way.
if you have a room with two people in it and randomly shoot a paintball into the room, there is a small risk of hitting one of the people the risk is there , certainly, but it is comparatively small. now in that same room, if you put 100 people that room and again, shoot a paintball gun into the room, the risk of hitting one of those people goes way up,....not down.
the cost of premiums is based on the risk of having to pay a loss on a claim,.... more people, the higher the likelyhood (risk) of paying on a claim,....so the premium goes up to increase investment to cover that higher potential of loss payout. insurance cos. would like you to think it doesn't, but it does and can only go one way,.....up. they aren't in business to pay claims without being compensated for it.
wake up, pull your head out of the sand and smell the coffee !.