大牛股一日腰斩，多只ETF被指接盘，指数投资隐藏何细节？

Core Viewpoint - The stock of Yaojie Ankang experienced extreme volatility on September 16, with a peak increase of 63% followed by a dramatic drop of 53.7%, resulting in a market value loss exceeding 190 billion HKD [2][5]. Company Overview - Yaojie Ankang, established in 2014, focuses on developing innovative small molecule therapies for cancer, inflammation, and cardiovascular metabolic diseases. The company currently has no commercialized products and reported losses of 343 million HKD and 275 million HKD for 2023 and 2024, respectively [5][6]. Stock Performance - The stock was listed on June 23, 2023, at an initial price of 13.15 HKD, and saw its value soar over 50 times, reaching a market capitalization close to 270 billion HKD, making it one of the top biotech firms in the Hong Kong market [3][5]. - On September 16, the stock price peaked at 679.5 HKD before closing at 192 HKD, marking a 72% decline from its intraday high [5][6]. ETF and Market Impact - Several ETFs tracking the National Index for Hong Kong Stock Connect Innovation were implicated in high-level buying during the stock's surge, raising concerns about their role as "bag holders" after the price drop [6][9]. - The National Index for Hong Kong Stock Connect Innovation saw a decline of 3.86% on the same day, with corresponding ETFs experiencing significant losses, indicating a direct impact from Yaojie Ankang's stock volatility [7][8]. Market Dynamics - The stock's rapid rise was attributed to limited liquidity, with only 549,000 shares available for trading, which allowed small amounts of capital to cause significant price fluctuations [6]. - The lack of transparency regarding the inclusion of Yaojie Ankang in the ETF indices has raised concerns among investors, potentially affecting their confidence and leading to unanticipated losses [9].