Just a couple of years ago it became known that Wellpoint was using the wrong actuarial table for their rate increase. Wellpoint is one of the top carriers.
There is no reason why the carriers cannot be transparent on this topic.
Actuarial tables are used for base rates and health care trends. Beyond that, unless things have changed dramatically, their tier their smaller groups to set the general guidelines for increases. Fully pooled groups are assigned risk factors, plus or minus, in as many as 10 different sub-groups.
Even still, the market determines what the real price is, not the carrier.