For the U.S. Presidential Primary allocation system, see American Plan.
The American Plan is the term that most U.S. employers in the 1920s used to describe their policy of refusing to negotiate with unions. The policy promoted union-free "open shops," where workers would not be required to join a labor union. It was endorsed by the National Association of Manufacturers in 1920. As a consequence of companies' promoting the "American Plan," as well as Supreme Court decisions hostile to labor, union membership shrank from 5.1 million in 1920 to 3.6 million by 1929.
[1] Summary of the American Plan in the Encyclopedia of Chicago.