. Matching workers to employers proceeded in four steps. First, we standardized the geographic and industry codes in the two data sets. Next, we selected all establishments that were unique in an industry-location cell. Third, all workers who indicated they worked in the same industry-location cell as a unique establishment were matched to the establishment. Finally, we eliminated all matches based on imputed data. The resulting data set is what we call the NWECD.There are a number of issues involved in the matching process that merit further discussion. The first set of issues concerns standardizing the geographic and industry codes. The Census Bureau divides the country into a hierarchy of geographic areas. For our purposes the relevant areas are state, county, place, tract, and block. The Census Bureau assigns a unique code to every state in the country. Within each state the Census Bureau assigns a unique code to every county. The Census Bureau also assigns a unique place code to population centers with 2,500 or more people. Because these population centers are unique within a state, but can cross county boundaries, we can distinguish between areas in the same place located in different counties. Finally, the Census Bureau divides up populated counties into unique tracts and divides tracts up into unique blocks.(7) Thus, for an establishment located in a metropolitan area, the Census Bureau assigns a unique geographic code which identifies the state, county, place, tract, and block of the establishment. ...
