HKEX concluded in December 2019 to enhance the Pre-Opening Session (POS) and Volatility Control Mechanism (VCM) in its securities market. The enhancements to the POS auction mechanism involve adopting relevant features from the Closing Auction Session (CAS), to help improve price discovery and increase trading liquidity before the market opens. The VCM enhancements covers expanded stock coverage, tiered triggering thresholds and allowing multiple triggers in a later phase to further reduce risks caused by individual stocks’ price volatility, reflecting changes in international practice and regulatory guidance. This page focuses on the implementation details of the two initiatives.
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