Multistage probability sampling was utilized for all surveys. Sample sizes, oversampling targets, and other methodological parameters have changed periodically throughout the series. Among the major changes are the following: Prior to 1991, the sampling universe did not include Alaska and Hawaii, or group-quarters such as college dormitories or shelters. Numerous changes in the questionnaire and editing methods were undertaken during the 1994 survey. In 1999, the administration mode for substance use items changed from self-administered answer sheets to audio-computer assisted self-interview (ACASI); sample design changes were also introduced.25 In 2002, a $30 incentive was introduced, further sample design and protocol changes were made, and the survey name was changed from the “National Household Survey on Drug Abuse” to the “National Survey on Drug Use and Health”.
