Under the Affordable Care Act, small group health insurers can set premiums using only four rating factors: geographic area, age, family size, and tobacco use. Every other characteristic of your business or your employees—health history, claims experience, gender, industry, group size, how long you’ve been covered—is off the table. Age variation is capped at a 3:1 ratio, tobacco at 1.5:1, and because the factors multiply rather than add, the widest legal gap between the cheapest and most expensive premium for the same plan is 4.5 to 1.
Who These Rules Cover
Federal law defines a small employer as a business averaging 1 to 100 employees, but states can narrow the definition to 1 to 50, and most have.1GovInfo. 42 USC 18024 – Related Definitions2HealthCare.gov. Small Business and the Affordable Care Act Employee count is based on the prior calendar year’s average of full-time workers (30+ hours per week) plus full-time equivalents calculated from part-time hours.3Internal Revenue Service. Determining if an Employer Is an Applicable Large Employer
Two important boundaries. First, these rating protections apply only to fully insured plans. If your business self-funds its coverage and pays claims directly, or if you kept a grandfathered plan that predates the ACA, the rating factor rules don’t apply. Second, federal law is the floor, not the ceiling; states can and do impose tighter limits, so what appears on your renewal depends on your state.
What Insurers Cannot Use
The statute is blunt. Under 42 U.S.C. § 300gg, an insurer’s premium “shall not vary with respect to the particular plan or coverage involved by any other factor” beyond the four permitted ones.4Office of the Law Revision Counsel. 42 USC 300gg – Fair Health Insurance Premiums That single sentence rules out a long list of characteristics insurers historically used:
- Health status, medical history, current diagnoses, claims experience, genetic information, and disability
- Gender, which drove higher premiums for women before the ACA
- Industry and occupation—a roofing company and an accounting firm with the same demographics pay the same base rate
- Group size, so a 5-person firm and a 45-person firm can’t be charged differently for that reason
- Duration of coverage, meaning how long the group has been insured is irrelevant
This is where the ACA changed the practical experience of buying small group coverage. A single expensive diagnosis inside your workforce can no longer trigger a targeted renewal spike. The base premium is what’s called an adjusted community rate: it reflects the average cost of care across a defined region, not your group’s claims.5CMS. Market Rating Reforms
The Four Permitted Factors
Federal regulations at 45 CFR § 147.102 spell out exactly how each factor works.6eCFR. 45 CFR 147.102 – Fair Health Insurance Premiums
Geographic Rating Area
Each state draws its own geographic rating regions. A region might be a single county, a group of counties, or a metro area. Within a region, every small group buying the same plan starts from the same base rate. Between regions, rates can differ because provider costs and utilization differ. A business in a high-cost urban area will see a different base than one in a rural part of the same state, but two employers on the same block cannot be charged different base rates because of where they sit.
Age
Age is the factor that produces the most visible price differences. The federal cap limits the ratio between the oldest adult (age 64) and the youngest (age 21) to 3:1.4Office of the Law Revision Counsel. 42 USC 300gg – Fair Health Insurance Premiums If a 21-year-old pays $250 a month, the most a 64-year-old can be charged for the same plan is $750.
The rise between those two points isn’t a straight line. The federal government publishes a standard age curve assigning a specific factor to every age from 0 through 64. It starts at 0.765 for children under 15, hits 1.000 at age 21, reaches 1.278 at 40, 1.786 at 50, 2.230 at 55, and tops out at 3.000 at age 64.7CMS. State Specific Age Curve Variations The steepest increases are in the 50s and 60s. A person’s age for rating purposes is fixed at the date of policy issuance or renewal, not the date they use care.6eCFR. 45 CFR 147.102 – Fair Health Insurance Premiums
Family Size
Premiums can differ by how many people the coverage includes. Under the federal default (per-member rating), the insurer calculates a separate premium for each covered family member using the age curve, then adds them up. One cost cap is built in: only the three oldest children under 21 are counted. A family with four or five kids pays the same as a family with three.6eCFR. 45 CFR 147.102 – Fair Health Insurance Premiums
Tobacco Use
Tobacco use is capped at a 1.5:1 ratio. A tobacco user can be charged up to 50% more than an otherwise identical non-user for the same plan.4Office of the Law Revision Counsel. 42 USC 300gg – Fair Health Insurance Premiums The regulatory definition of tobacco use is specific: any tobacco product, on average four or more times per week, within the past six months. Occasional social use doesn’t count, and religious or ceremonial use is explicitly excluded.6eCFR. 45 CFR 147.102 – Fair Health Insurance Premiums
In the small group market, any tobacco surcharge is also subject to the ACA’s wellness program rules. The insurer must offer a reasonable alternative standard, typically a cessation program, that lets an employee avoid the surcharge.8U.S. Department of Labor. HIPAA and the Affordable Care Act Wellness Program Requirements The maximum reward or penalty tied to tobacco is 50% of the cost of coverage, higher than the 30% ceiling for other health-contingent wellness programs.9Federal Register. Incentives for Nondiscriminatory Wellness Programs in Group Health Plans Plan materials have to disclose the alternative clearly.
How the Factors Combine
Age, tobacco, and geography multiply rather than add. Multiply the 3.0 age ceiling by the 1.5 tobacco ceiling and the widest legal age-plus-tobacco variation is 4.5:1.10Federal Register. Patient Protection and Affordable Care Act – Health Insurance Market Rules Rate Review In real numbers: if a 21-year-old non-user pays $250 a month, a 64-year-old tobacco user on the same plan in the same area could pay up to $1,125. Geography stacks on top, which is why identical plans from the same carrier can look very different across regions.
What You Actually See on a Quote
Most small group employers see a single composite rate per employee, not a per-person calculation. That’s allowed, but the math underneath still has to follow the per-member methodology. At the start of the plan year, the insurer calculates each covered person’s premium using the age curve, sums those across the group, and divides to produce the composite. That composite is locked for the plan year; it doesn’t change if someone joins or leaves mid-year.11eCFR. 45 CFR 147.102 – Fair Health Insurance Permiums
Under the federal default, composite rates use two tiers: one for adults 21 and older, one for people under 21. A group with a younger workforce will see a lower composite than an older workforce buying the same plan, but the underlying gap is still constrained by the 3:1 age cap on the individual-level math.
State Variations
Federal law sets the widest variation an insurer can produce; states can compress it. Some states require narrower age ratios than 3:1, and a handful mandate pure community rating, where age can’t affect price at all. Roughly a dozen states plus the District of Columbia have restricted or eliminated tobacco surcharges, either banning them outright or setting a ratio tighter than 1.5:1. What appears on your renewal follows your state’s rules, so treat the federal limits described here as the outer boundary of what you might see, not a prediction of what you will.