The MWTS covers the Wholesale Trade (Sector 42), excluding manufacturers' sales branches and offices. This sector has been designated by NAICS.
NAICS (North American Industry Classification System) is used to classify a business' primary activity. It replaced SIC (Standard Industry Classification).
For further business information regarding NAICS, you can access the following URL: http://www.census.gov/epcd/www/naics.html
Your firm was chosen from a scientifically selected sample of businesses. Taking a sample is less costly than contacting every business in the country. Smaller firms, which are selected for the sample represent other similarly sized businesses who do not report.
The sample is revised approximately every five years in order to relieve most firms from the burden of continually reporting. While the largest firms continue to be canvassed, most of the small and medium sized firms are not re-selected.