Both the benchmark levels and the sample-based estimates are subject to several sources of nonsampling error,
cheef among which are (1) the inability to measure employment in new firms from the time of their inception, due to the time lag between the creation of new firms and their inclusion in the sample; (2) the procedures for handling changes in industrial classification; (3) the quality of the various source data used to derive the benchmark; (4) the inability to cover completely all firms in the target population; and (5) other sources of errors in coverage, response, processing, and collection.