In 2003, three of Russia's leading investment, financial, and industrial groups - Alfa Group, Access Industries, and Renova - formed the AAR Consortium. AAR's key asset is its 50 percent share in TNK-BP. The Consortium represents the interests of the Russian shareholders in the oil company. One of the largest oil companies in Russia, TNK-BP was created through the merger of the oil and gas assets of BP in Russia and those of the AAR Consortium. The $15 billion merger with British Petroleum that established the company is the largest corporate transaction to date involving a Russian and foreign company. Being the third largest company in Russia, TNK-BP accounts for approximately 16% of Russia's oil production (including its half-ownership of Slavneft). By volume of oil produced, TNK-BP is one of the ten largest private oil companies in the world. The company produced 1.742 million barrels of oil per day, or 87 million tons annually. The independent audit conducted by DeGolyer and MacNaughton confirmed that as of 31 December 2010 TNK-BP's Total Proved Reserves amounted to 13.1 billion barrels of oil equivalent, applying PRMS (formerly SPE) criteria. Proved Reserves constitute a Total Proved PRMS reserve replacement ratio of 322%. The company's upstream operations are located in Western and Eastern Siberia and in the Volga-Urals region. TNK-BP owns and operates five refineries in Russia and Ukraine, and retails through a network of about 1.500 filling stations.