My comment: The latest data available is for the year of 2007.
(i) Small & Medium-Sized Exporting Companies:
Statistical Overview, 2007. International Trade Administration, US Department of Commerce,
http://ita.doc.gov/td/industry/otea/sme_2007/SME_index_2007.htm
(2) Press Release: A Profile of U.S. Exporting Companies, 2006 - 2007. U.S. Census Bureau and Department of Commerce, Apr. 9, 2009.
http://www.census.gov/foreign-trade/Press-Release/edb/2007/text.txt
Check the section "Who Exports?" ("Exhibit 1a shows that manufacturers accounted for the largest portion of the 2007 known value, 65
percent")