Improving survey participation

The general decrease in telephone survey response rates leads to potential selection and estimation biases. As nonrespondents can be broken down into noncontacts and refusals, different strategies can be deployed - increasing the number of call attempts before abandoning a number, and calling back refusals/abandonments to persuade them to participate. Using a two-stage random-digit-dialing sample of 8,645 individuals aged 15-49 for a survey on sexual and reproductive health (SRH), we compared the effects of the two strategies: including hard-to-contact respondents (more than twenty call attempts with no upper limit) and including respondents from two successive waves of call-back among initial refusals/abandonments. Comparisons were based on sociodemographic bias, differences in SRH behaviors, multivariate logistic modeling of SRH behaviors, post-calibration weighting, and cost estimation. The sociodemographic profile of hard-to-contact and call-back respondents differed from that of easy-to-interview respondents. Including hard-to-contact respondents decreased the socio- demographic bias of the sample, while including call-back respondents increased it. Several significant differences in SRH behaviors emerged between easy-to-interview and hard-to-contact respondents, but none between first-wave and call-back respondents. Nevertheless, the determinants of SRH behaviors in call-back and hard-to-contact respondents differed with respect to easy-to-interview respondents. The trade-off between bias and financial costs suggests that the best protocol would be to mix the two strategies but with only one call-back wave involving a limited number of call attempts to achieve a sufficient sample size with optimal quality.