[Methoden] ESRA 2019: Sampling Hard-to-Reach Populations (CfA)

-- Prof. Dr. Ulrich Kohler University of Potsdam Public interest in learning more about demographic groups that are either small, hidden, mobile, or engaged in illicit behaviors has grown in recent years. Prominent examples of these “hard-to-reach” populations are drug addicts, homeless people, or prostitutes as well as very rich people and migrants, particularly those who are not documented or who travel a lot. None of these demographic groups can be adequately sampled with probability surveys, either because of the absence of sampling frames, the small size of these groups compared to the total population, their unstable residency, or their reluctance to participate. In order to learn more about these hard-to-reach populations, researchers have employed a few different sampling methods, including network sampling, link-tracing designs (aka snowball sampling), and respondent-driven sampling. Although the use of such nonprobability sampling methods to survey hard-to-reach groups has rapidly expanded and has been employed in many different contexts (though particularly in developing countries), numerous questions regarding both the implementation of these surveys and the analyses of the collected data have not yet been (fully) resolved. o How can the target population be adequately delineated and identified in the sampling process? o How should researchers choose incentives and interview locations when surveying hard-to-reach populations? What are best practices in seed selection? o What do we know about mode differences when surveying hard-to-reach populations and asking individuals about illicit behaviors? o What challenges occur when employing nonprobability sampling in comparative studies, for example with regard to the number of initial seeds and assumptions regarding the referral o What are the best estimators when analyzing data collected from non-probability samples? o How can we best calculate the variability of the estimates from non-probability samples? o What are the ethical issues when surveying hard-to-reach populations and how can they be resolved in an acceptable way for researchers, respondents, and funding agencies? o How can nonprobability surveys be combined with other methodological approaches to assess the accuracy of their findings?