* Since 2007, CBP has used Noise Infusion for this data as a method of disclosure avoidance. This new method allowed disclosure of data for many more counties, which may affect the national median value. Prior to 2007, data were protected using the complementary cell suppression method. For more information on Noise Infusion and Suppression, see the Source tab.
Years Available: 1998–2017
Permanent Link: http://data.sagepub.com/sagestats/4786
General Notes: Industry code NAICS 48-49. *Median value gives the value for the "average" county for this metric, the 50th percentile of all counties reporting data.