Consistent measures are imperative for conducting valid historical analyses. Collected in the long-form survey of the decennial census, employment data has traditionally been tabulated by aggregate industrial category for all counties. Starting in 2000, the industrial coding scheme drastically changed. In response, we develop a methodology to formulate “geographically-sensitive” conversion factors that reconfigure NAISC-based tabulations into long-established SIC categories.This research has been supported by Grant Number P01 HD045753 from the National Institute of Child Health and Human Development.http://deepblue.lib.umich.edu/bitstream/2027.42/57739/1/ICPSR-WP-No1-Witkowksi-Gutmann.pd