3% 100m shares to 4% 130m is based on Direct ASX S&P 200 inclusion meaning volume from both trackers of ASX 200 and 300
Current SP200 constituents with MKT of $3b have 0.15% weighting
AVZ will get bigger bump becuase it is entering both ASX 200 and ASX 300 since AVZ is not in either.
Normally a stock enters ASX 300 with a bump in volume and creeps up to when it enters ASX 200 (funds that track ASX 300 will need to buy incremental but ASX 200 tracking will wade in for the first time)
Dont forget it gets included to MCSI ACWI index (and others), meaning managers all around the world that track international funds will also have to buy a clip. It will be a tiny portion but when there are tens of thousands in US, EU and Asia that do track it for their domicled etf and pensions funds it adds up.
ie Australian Super default funds
Australian Shares option track ASX 300 International Shares option tracks MCSI ACWI ex Australia
(20min delay)