exposure with the observed exposure. From the total sample of N=196,620 observations, 72.4% resided in their state of birth, leaving 27.6% susceptible to misclassification when using the state-of-birth proxy. However, imputed MLDA exposure matched observed MLDA exposure in 88.0% of subjects, indicating that 15.6% of the population had emigrated to states with similar MLDA policy as their birth state. Using the proxy approach to predict observed exposure, the positive predictive value was 88.4%, while the negative predictive value was 87.4%. (These values correspond to the percentage of correctly classified exposed and unexposed individuals, respectively). Hence, this approximation appears to exhibit little bias towards positive or negative misclassification, and exhibits good overall precision. These analyses are discussed in more detail in the Supplemental Material.
