Impact of correcting for nonresponse by weighting on estimates of alcohol consumption.

OBJECTIVE: This study describes the characteristics of nonrespondents and assesses the impact of unit nonresponse on estimates of central alcohol consumption variables by examining the impact of corrective weighting.
METHOD: The data came from a Finnish general population random sample of 1,932 respondents (987 women) (response rate: 78.1%). The survey was carried out in the year 2000 using face-to-face interviews. The impact of unit nonresponse was assessed by comparing results using (1) no weighting; (2) poststratified weights adjusted for age, gender and region; (3) weights obtained from a statistical model predicting response propensity; and (4) weights from the model, adjusted to match the population distribution for age, gender and region. Extensive auxiliary information used to predict response propensity came from administrative registers.
RESULTS: Compared with respondents, both male and female nonrespondents had fewer children, lived in urban areas and lived in southern Finland. Male nonrespondents were also older; female nonrespondents more often had only a basic education and were less often in the second-highest income quartile. The change in alcohol variables resulting from the adjustment for nonresponse was small, however, and the difference between the different weighting schemes was even smaller.
CONCLUSIONS: If nonrespondents' drinking differs considerably from that of respondents, this difference cannot be captured even by using extensive auxiliary information and an elaborate model predicting propensity of nonresponse.