[["( in millions )", "2011", "2010", "2009"], ["sales and transfers of oil and gas produced net of production and administrative costs", "$ -7922 ( 7922 )", "$ -6330 ( 6330 )", "$ -4876 ( 4876 )"], ["net changes in prices and production and administrative costs related to future production", "12313", "9843", "4840"], ["extensions discoveries and improved recovery less related costs", "1454", "1268", "1399"], ["development costs incurred during the period", "1899", "2546", "2786"], ["changes in estimated