Does the sampling method use stratification?
Yes. A multistage probability sample was employed to draw the sample of dwelling units. First, a list of 2,029 consolidated raions (similar to counties) was created from which to draw primary sample units (PSUs). These were allocated into 38 strata based largely on geographical factors and level of urbanization, but also based on ethnicity where there was salient variability. As in many national surveys involving face-to-face interviews, some remote areas were eliminated to contain costs; also, Chechnya was eliminated due to armed conflict. From among the remaining raions (containing more than 95.5% of the population), three very large population units were selected with certainty: Moscow city, Moscow Oblast, and St. Petersburg city each constituted a self-representing (SR) stratum. The remaining non-self-representing raions (NSRs) were allocated to 35 strata of roughly equal size. One raion was then selected from each NSR stratum using the method “probability proportional to size” (PP
