Source: Cameron AC, Trivendi PK 2010. Microeconomics using stata. Ch14
The data come from wave 5 (2002) of the Health and Retirement Study (HRS), a panel survey sponsored by the National Institute of Aging. The sample is restricted to Medicare beneficiaries. The HRS contains information on a variety of medical service uses. The elderly can obtain supplementary insurance coverage eigher by purchasing it themselves or by joining employer-sponsored plans.