Abstract
This report documents a statistical procedure, called imputation, that was implemented in the National Accident Sampling System (NASS) General Estimates System (GES). Imputation is a method of replacing unknown data with known data on a case by case basis. This document gives an overview of the imputation process, why it was implemented, how imputed values are best not used. This report provides users of the GES datafile with the information necessary for better understanding of the GES data. (A)