What is the main difference between individual and group health insurance underwriting?

Group health insurance pools risk across all members of a group (typically employees of a company) and historically has used minimal individual medical underwriting — anyone in the group qualifies based on employment. Premiums are based on the group's overall demographics and claims experience. Individual health insurance under ACA rules is community-rated (premiums based only on age, geographic area, family size, and tobacco use — not health status) and 'guaranteed issue' (no one can be denied for health reasons). Before the ACA, individual policies used full medical underwriting and could exclude or rate up for health conditions. Group policies typically offer more comprehensive coverage at lower per-person cost due to risk pooling and employer contribution.