This method contrasts with two other network-related at-tempts to estimate total population size: 1) network scale-up methods and 2) other capture-recapture methods using multiple RDS samples. In the words of a recent summary, network scale-up methods (or NSUM) “rests on the assumption that people’s social networks—the set of people whom you ‘know’ —are, on average, representative of the general population in which you live and move” (Bernard et al., 2010: p. ii12). In this procedure, individual estimates of sub-populations are “scaled” to aggregate levels, and the estimates of many individuals are combined. For example, if a respondent answers that he/she knows two pregnant women out of a total of 100 contacts, we could estimate the number of pregnant women in his/her county of 10,000 people (via consistent proportion) to be 200. By combining this estimate with the estimates drawn from many others, more accurate figures can be obtained. NSUM advo- cates see this as a means for estimating the size of sub-popula- tions that may be known but difficult to enumerate. Still, sig- nificant problems arise for NSUM methods when trying to estimate rates of participation in activities that individuals