13A probabilistic sample of the population of approximately 500 aged 15 years or older was drawn from each city. The 2008 survey involved Computer Assisted Telephone Interviews (CATI) conducted with n=8,155 (including 1,500 residents from outside the twelve cities who were aged 15 years and older). Quotas were set for ethnicity, age, location and gender. Respondents were selected randomly from the Electoral Roll and a pre-notification letter was sent to potential respondents, who were contacted by phone for the interviewing. Fieldwork was conducted between 16 July and 28 October 2008. The average duration of the interviews was 20.3 minutes and the final response rate was 37 percent.