premise: Because pork production in Sonora is a relatively new development and because the United States has restricted the importation of swine and pork products for the last 20 years, APHIS bases its potential impact analysis on some assumptions regarding the level of pork production in Sonora in the future, the percentage of pork production that might be processed in Sonora for shipment to the United States, and the demand for pork in the United States.
hypothesis: For the last 20 years the United States has placed restrictions on pork products being imported.