Group 1 - Citigroup completed a significant share purchase of 225,000 shares at an average price of HKD 417.24 per share, totaling approximately HKD 939 million, increasing its total holdings to 63.49 million shares, representing 5% of the issued shares [1] - This increase in shareholding positions Citigroup as the second-largest shareholder, just behind the Hong Kong SAR government, which holds 5.9% [1] - The shareholding structure of the Hong Kong Stock Exchange (HKEX) is relatively dispersed, with a high proportion of institutional investors, and Citigroup's actions have altered the dynamics among major shareholders [2] Group 2 - The Hong Kong stock market has seen a significant increase in trading volume and activity this year, with net inflows from southbound funds exceeding the total for the previous year [3] - The average daily trading amount for Hong Kong stocks reached HKD 240.2 billion in the first half of the year, a year-on-year increase of 118%, marking the highest level since 2010 [3] - The profitability of HKEX is highly correlated with trading volume and turnover, and Citigroup's increased shareholding aligns with the improved fundamentals of the exchange [3]