Appendix 1 Survey Methodology I. Survey Methodology (I) Survey on Individual Internet Users 1.1 Survey Population Permanent residents at the age of 6 or above who have residence fixed-line telephones (including home phones, PHS and dormitory telephones) or mobile phones ◇ Sample size There were 60,000 survey samples in total covering 31 provinces, autonomous regions and municipalities directly under the central government in Mainland China. ◇ Division of survey population survey population A B C subpopulation subpopulation with subpopulation with residence both fixed-line with fixed-line telephone and mobile phones telephones mobile phones The survey population can be divided into three categories: Subpopulation A: Survey subpopulation using residence fixed-line telephones (including residents with home phones, PHS users, students with dormitory telephones, and other users with dormitory telephones); Subpopulation B: Survey subpopulation with mobile phones; Subpopulation C: Survey subpopulation with both residence fixed-line telephones and mobile phones (there is an overlap between subpopulation A and subpopulation B, and the overlapped part is subpopulation C), C=A∩B. 1.2 Sampling Method CNNIC surveys subpopulation A, B and C. Double sampling is adopted for the survey so as 111111 The 39th Statistical Report on Internet Development in China