More than 2,000 individuals from over 300 families responded to the original 1971 questionnaire mailed from the University of Southern California. These families were recruited by enlisting a grandfather over the age of 60 who was part of a three-generation family willing to participate. Grandchildren were age 16 to 26. Families were drawn randomly from a subscriber list of 840,000 members of a California Health Maintenance Organization in Los Angeles.
    Now, 25 years later, one-half of the families still remain in California. The rest are scattered across the country and two percent live abroad. Most geographic mobility has taken place in the third and fourth generation. At the most recent data collection, 1,678 members participated in the study, some spouses and great-grandchildren of the original members.