Group underwriting evaluates the group as a whole, not each person in it. There are no individual medical exams; the underwriter studies the characteristics of the group. That is the core difference from individual underwriting, where each applicant's own health history is reviewed.

Occupational class: the kind of work a group does affects how often and how severely its members are expected to have claims. A roofing contractor and an accounting firm with the same head count and ages may be priced differently. Hazardous occupations are not barred from group coverage; occupation is weighed in the underwriting.

Group size and prior claims experience: the more people and claims a group has, the more statistically reliable its own past results are, so a large group's claims history can carry more weight in its rate. In a small group, one or two large claims can distort the record.

Contrast with small groups: the premium for a nongrandfathered small employer health plan may vary only by age, geographic region, and whether the plan covers an individual or a family (§10753.14). Any other factor, including the group's claims experience, is barred.