LONDON -(Dow Jones)- Deals between national oil companies and traders should be disclosed as part of the Extractive Industries Transparency Initiative, or EITI, according to a report by the Revenue Watch Institute published Monday. "National oil companies and the buyers of their oil should publish the price, volume, and crude grade for every cargo of oil sold," the report said. Greater transparency requirements could have a significant effect on large, Swiss-based oil trading firms, such as Trafigura Group, Glencore International PLC (GLEN.LN), Vitol Holding and Mercuria, as well as oil majors BP PLC (BP), Royal Dutch Shell PLC (RDSA) and Total SA (TOT). The Revenue Watch Institute is a non-profit organization involved with the EITI, a voluntary scheme started 10 years ago to improve transparency in the natural resources industry. "Since oil marketed by state companies belongs to the citizens of those countries, national oil companies and buyers share responsibility for making public all sales information," said Alexandra Gillies, head of governance at Revenue Watch and leader of its research project. -By Sarah Kent, Dow Jones Newswires;4420-7842-9376; sarah.kent@dowjones.com