(d) Small employer carriers shall apply rating factors consistently with respect to all small employers. Rating factors shall produce premiums for identical groups that differ only by the amounts attributable to plan design and do not reflect differences due to the nature of the groups assumed to select particular health benefit plans. Two groups that are otherwise identical, but which have different prior year rate factors may, however, have rating factors that produce premiums that differ because of the requirements of subsection (a)(6) of this section. Nothing in this section shall be construed to prevent a group health plan and a health insurance carrier offering health insurance coverage from establishing premium discounts or rebates or modifying otherwise applicable copayments or deductibles in return for adherence to programs of health promotion and disease prevention, including those included in affordable health benefit plans, provided that the resulting rates comply with the other requirements of this section, including subsection (a)(4) of this section. The calculation of premium discounts, rebates, or modifications to otherwise applicable copayments or deductibles for affordable health benefit plans shall be made in a manner consistent with accepted actuarial standards and based on actual or reasonably anticipated small employer claims experience. As used in the preceding sentence, "accepted actuarial standards" includes actuarially appropriate use of relevant data from outside the claims experience of small employers covered by affordable health plans, including, but not limited to, experience derived from the large group market, as this term is defined in § 27-18.6-2.