Core Points - The CSI All Share Oil and Gas Extraction and Oilfield Services Index opened at 3989.28 points and has seen a decline of 2.47% in the past month, 1.93% in the past three months, and 6.22% year-to-date [1] - The index is designed to reflect the overall performance of different industry companies within the CSI All Share Index, categorized into 11 primary industries, 35 secondary industries, over 90 tertiary industries, and more than 200 quaternary industries [1] Index Composition - The top ten weighted companies in the CSI All Share Oil and Gas Extraction and Oilfield Services Index are: CNOOC Engineering (14.9%), Jereh (14.77%), CNOOC Development (9.84%), China Oilfield Services (9.69%), Sinopec Oilfield Service (9.31%), China National Petroleum Engineering (6.66%), Hongtian (3.84%), Sinopec Machinery (3.69%), Deweier (2.98%), and Haimer Technology (2.96%) [1] - The market segments of the index holdings show that the Shanghai Stock Exchange accounts for 62.59%, the Shenzhen Stock Exchange for 36.79%, and the Beijing Stock Exchange for 0.62% [2] - In terms of industry composition, oilfield services represent 50.78% and oil and gas extraction represent 49.22% of the index holdings [2] Index Adjustment - The index samples are adjusted semi-annually, with adjustments implemented on the next trading day following the second Friday of June and December each year [2] - Weight factors are adjusted in accordance with the sample adjustments, which are generally fixed until the next scheduled adjustment [2] - Temporary adjustments occur when the CSI All Share Index samples are modified, and changes in industry classification due to special events will also prompt corresponding adjustments in the index samples [2]