title: [Study on using the multiplier method in estimating the size of men who have sex with men population in Shanghai].
abstract: OBJECTIVE
  To estimate the size of men who have sex with men (MSM) in Shanghai.
  
  
  METHODS
  Multiplier method was used in the study and two popular Shanghai-based MSM websites were selected as targeted institutions. The number of MSM (r) who visited website during a given period was investigated by a web-based questionnaire. Meanwhile, a survey was conducted among MSM living in Shanghai to obtain the proportion of MSM who had visited the websites during the given period, the reciprocal number of this proportion was the multiplier (m), therefore, population size can be estimated by r multiplied by m.
  
  
  RESULTS
  The MSM population was estimated as 398 433 when website A was selected as target institution and 370 755 was estimated when website B was selected. The estimated population of MSM accounted for 7.1% and 6.6% of male population aged 15 to 49 years old in Shanghai, respectively.
  
  
  CONCLUSIONS
  It was feasible to use multiplier method which selecting MSM website as target institution to estimate the size of MSM population, however, the representativeness of this study sample should be considered seriously.
authors.affiliation: Department of AIDS/STD Control and Prevention, Shanghai Municipal Center for Disease Control and Prevention, Shanghai 200336, China.
authors.forename: Zhen
authors.initials: Z
authors.lastname: Ning
authors.forename: Qi-Chao
authors.initials: QC
authors.lastname: Pan
authors.forename: Xiao-Hong
authors.initials: XH
authors.lastname: Zheng
authors.forename: Wei
authors.initials: W
authors.lastname: Zhang
authors.forename: Fan
authors.initials: F
authors.lastname: Lv
authors.forename: Lai-Yi
authors.initials: LY
authors.lastname: Kang
mesh_terms: D000293:Adolescent; D000328:Adult; D002681:China; D003625:Data Collection / Q000379:methods*; D018451:Homosexuality, Male / Q000706:statistics & numerical data*; D006801:Humans; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D011156:Population Density; D011795:Surveys and Questionnaires; D014505:Urban Population; D055815:Young Adult