Shein (0625 HK) will join the Hang Seng Composite Index, effective 15th September

Index inclusion is a well-worn flow event in Hong Kong, where the Hang Seng Composite is the gateway rather than the destination: membership is the prerequisite for Stock Connect eligibility, which historically has been the larger liquidity event for newly added names, since it opens the name to mainland southbound flows. The usual sequence is a front-run accumulation window into the effective date, passive buying clustered at the close of the rebalance day, and a partial give-back in the sessions that follow as the flow premium unwinds. The distinction worth drawing is between the mechanical index demand, which is estimable from tracker AUM and the name's eventual weighting, and the discretionary repositioning, which is not. For a large recent listing of this profile, free-float and weighting-band treatment determine how much passive money actually has to buy, and the index provider's follow-on notices on Stock Connect inclusion are the next dated catalyst. Volume patterns into the effective date, particularly closing-auction prints, have tended to be the cleanest tell of how much of the flow was pre-positioned.