Population size estimation of men who have sex with men using Google Trends search data. (Preprint)

BACKGROUND Population size estimation (PSE) for key populations is needed to inform HIV programming and policy. We examined the potential utility of applying a recently proposed method using Google Trend (GT) internet search data to generate PSE (GTPSE) for men who have sex with men (MSM) in 54 countries in Africa, Asia, the Americas, and Europe. OBJECTIVE To examine the utility and plausibility of using Google Trends data to generate PSE in 54 LMICs. METHODS Applying a newly proposed PSE method, we examined GT relative search volumes (RSV, representing the relative internet search frequency of specific search terms) for “porn” and, as a comparator term, “gay porn” for the year 2020. We assumed the term “porn” represents “men” (denominator) while “gay porn” represents a subset of “MSM” (numerator) in each county, resulting in a proportional size estimate for MSM. We multiplied the proportional GTPSE values with countries’ male adult population (15-49 years) to obtain absolute size estimates. Separately, we produced subnational MSM PSE limited to countries’ (commercial) capitals. Using linear regression analysis, we examined the effect of countries’ level of urbanization, internet penetration, criminalization of homosexuality, and stigma on national GTPSE results. We examined key assumptions of the proposed model. Further, we conducted a sensitivity analysis in a subset of countries (n=14) examining the effect of alternative English search terms, different language search terms (Spanish, French, Swahili), and alternative search years (2019, 2021). RESULTS One country was excluded from our analysis as no GT data could be obtained. Of the remaining 53 countries, all national GTPSE values exceeded the World Health Organization’s (WHO) recommended minimum PSE threshold of 1% (range: 1.2%-7.5%). For 44/49 (89.8%) of countries, GTPSE results were higher than UNAIDS KP Atlas values but largely consistent with the regional UNAIDS Global AIDS Monitoring results. Substantial heterogeneity across same-region countries was evident in GTPSE although smaller than those based on KP Atlas data. Subnational GTPSE values could be obtained in 51/53 (96%) countries; all subnational GTPSE values exceeded 1% but often did not match or exceed the corresponding countries’ national estimates. None of the covariates examined had a substantial effect on the GTPSE values (R2 values 0.01-0.28). Alternative (English) search terms in 12/14 (85%) countries produced GTPSE >1%. Using non-English language terms often produced markedly lower same-country GTPSE values compared to English with 10/14 (71%) countries showing national GTPSE exceeding 1%. GTPSE using 2019 and 2021 search data produced similar results as the reference year 2020. Due to lack of absolute search volume data, credibility intervals could not be computed. The validity of key assumptions, especially who (males, females) searches for porn and gay porn, could not be assessed. CONCLUSIONS GT-based PSE for MSM provides a simple, fast, virtually cost-free method. Limitations include the lack of validation of key assumptions, and inability to assign credibility intervals. GTPSE for MSM may provide an additional data source, especially for estimating national-level PSE.