Response propensity is the theoretical probability that a sampled person (or unit) will become a respondent in a specifie survey. Sampled persons differ in their likelihood to become a respondent in a survey. These differences are a result of the fact that some persons are easier to get into contact with than are others, some persons are more willing and able to participate in a specific survey than others, or both. Response propensity is an important concept in survey research, as it shapes the amount and structure of unit nonresponse in a survey. The covariance between response propensity and the survey variable of interest determines the bias in survey estimates due to nonresponse. Theoretically, using response propensities, a researcher could entirely correct for nonresponse bias. ...