U.S. Citizenship and Immigration Services has an online explanation of the annual caps set by Congress on certain nonimmigrant visa classifications used by employers to bring in foreign workers in specialty or other occupations (H-1B and H-2B visas). The explanation also provides an update on its rule prohibiting duplicate filings of H-1B petitions by employers; as of June 6, 2008, USCIS found that less than ½ of one percent of the total H-1B eligible petitions received involved duplicate filings for the same prospective beneficiary.