On the wrong side of the tracts? Evaluating the accuracy of geocoding in public health research

Objectives. This study sought to determine the accuracy of geocoding for public health databases. Methods. A test file of 70 addresses,, 50 of which involved errors, was generated, and the file was geocoded to the census tract and block group levels by 4 commercial geocoding firms. Also, the "real world" accuracy of the best-performing firm was evaluated. Results. Accuracy rates in regard to geocoding of the test file ranged from. 44% (95% confidence interval [Cl] = 32%, 56%) to 84% (95% CI = 73%, 92%). The geocoding fu-m identified as having the best accuracy rate correctly geocoded 96% of the addresses obtained from the public health databases. Conclusions, Public health studies involving geocoded databases should. evaluate and report on methods used to verify accuracy.