When citing the Economic Policy Institute, a Washington, D.C.-based think tank, mainstream journalists often affix the label "union-backed" or "labor-supported" (e.g. New York Times, 3/13/94). By contrast, these reporters rarely if ever refer to the American Enterprise Institute as "corporate-backed" or "business-supported." (A search on the Nexis database turned up 73 instances where major papers use such labels with EPI, whereas similar terms were used with AEI--which is cited far more frequently--only 4 times.)
As it happens, only about a quarter of EPI's money comes from labor, whereas more than half of AEI's funding comes from corporations and corporate foundations. Furthermore, AEI was organized back in 1943 with the explicit mission of getting the business voice heard. Its leader in its growth phase, William Baroody, Sr., came directly from the U.S. Chamber of Commerce, and AEI was notable for its "early and close relationship" with the Business Roundtable, according to John Saloma's Ominous Politics.
Why, then, the differential treatment? It would appear that reporters have internalized the view of the corporations and their acolytes that labor is a "special interest," whereas the corporations that support AEI represent the "national interest."