Respondent-driven sampling (RDS) is a method for recruiting “hidden” populations through a network-based, chain and peer referral process. RDS recruits hidden populations more effectively than other sampling methods and promises to generate unbiased estimates of their characteristics. RDS’s faithful representation of hidden populations relies on the validity of core assumptions regarding the unobserved referral process. With empirical recruitment data from an RDS study of female sex workers (FSWs) in Shanghai, we assess the RDS assumption that participants recruit nonpreferentially from among their network alters. We also present a bootstrap method for constructing the confidence intervals around RDS estimates. This approach uniquely incorporates real-world features of the population under study (e.g., the sample’s observed branching structure). We then extend this approach to approximate the distribution of RDS estimates under various peer recruitment scenarios consistent with the data as a means to quantify the impact of recruitment bias and of rejection bias on the RDS estimates. We find that the hierarchical social organization of FSWs leads to recruitment biases by constraining RDS recruitment across social classes and introducing bias in the RDS estimates.

Of a total of 528 729 workers exposed to benzene or benzene mixtures in China, 508 818 (96-23%) were examined. Altogether 2 676 cases of benzene poisoning were found, a prevalence of 0-51 %. A higher prevalence of benzene poisoning was found in the cities of Hangjou, Hefei, Nanjing, Shenyang, and Xian. The geometric mean concentration of benzene in 50 255 workplaces was 18 1 mg/m3 but 64-6% of the workplaces had less than 40 mg/m3. There was a positive correlation between the prevalence of benzene poisoning and the concentration in shoemaking factories. The prevalence of benzene induced aplastic anaemia in shoemakers was about 5 8 times that occurring in the general population. The results of this investigation show the need for a practicable hygiene standard to prevent benzene poisoning.

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Pollard and Morgan (2002) argued that the parental mixed‐gender preference (i.e., parents' preference to have at least one son and one daughter) will weaken in the United States as aspects of gender become increasingly deinstitutionalized. They presented evidence that mixed‐gender preference weakened in the 1986–1995 period compared to earlier and coined this change as emerging gender indifference. On the other hand, credible claims and evidence suggest that after 1985, the “gender revolution” has stalled. Such arguments suggest that weakened mixed‐gender preference will persist. In this study, the authors replicated and extended Pollard and Morgan using 4 waves of data from the National Survey of Family Growth that allow examination of the 1966–2009 period. The results show that the effect of same‐gender children on intending/having another child declined in the 1986–1995 period; however, no evidence that this effect has continued to weaken was found. Thus, these data show evidence consistent with a “stalled revolution.”