Source and References

U.S. Census Bureau, A Profile of U.S. Importing and Exporting Companies, 2012-2013

U.S Census Bureau, 2013 County Business Patterns (CBP). For more information on the data used in the CBP and accuracy of the data see http://www.census.gov/econ/cbp/methodology.htm

Current Population Survey (CPS). 2013 Annual Social and Economic Supplement. For more information on the data used in the CPS and accuracy of the data see http://www.census.gov/cps/methodology/

2013 Annual Survey of Manufactures (ASM). For more information on the data used in the ASM and accuracy of the data see
http://www.census.gov/manufacturing/asm/how_the_data_are_collected/index.html

A Profile of U.S. Importing and Exporting Companies, 2012-2013 For more information on the data used in the Profile of U.S. Importing and Exporting Companies and accuracy of the data see http://www.census.gov/foreign-trade/guide/sec2.html#source