Appendix: Methodology.

The 1993 AGI survey of health insurers had three components: commercial insurance companies, Blue Cross/Blue Shield plans and health maintenance organizations (HMOs). The survey instruments used for the first two were identical. The survey for the HMOs included identical questions on the coverage

Components

The procedure and response rates were similar for the three components of the study.

Commercial insurance companies

The commercial insurance survey was sent to the 100 largest commercial insurance companies in the United States based on the ranking of insurance companies, according to their net accident and health premiums written included in National Underwriters Profiles: 1993 Health Insurers. (1) The name and address of the chief executive officer (CEO) of each insurance company was obtained from Best's Insurance Reports: Life/Health Edition. (2)

Data in National Underwriters Profiles on the total net accident and health premiums written for all insurers were used to calculate the share of the total health insurance market that was covered by the sample of the 100 largest commercial insurers. Together, these insurers accounted for 97% of total net accident and health premiums written by all insurers.

The 12-page survey instrument was mailed to the CEO of each insurer on October 19, 1993. A second mailing was sent on November 12, and telephone follow-up both to obtain additional responses and to clarify issues arising from responses continued through December 1993.

Insurers were given the following instructions for completing the questionnaire: "Please answer the questions pertaining to your policy/contract written for groups to cover employees and their dependents in 1993. These questions do not apply to coverage written for persons not part of a group or to coverage supplementing Medicare benefits."

There are five types of policies/contracts that commercial insurance companies and Blue Cross/Blue Shield plans write and the survey was divided into five parts, essentially repeating a single set of questions for each type of policy/contract: