It usually is - changes are moderately predictable and investors...

It usually is - changes are moderately predictable and investors often try to front run either the announcement of the changes to Index composition and/or the effective date of inclusion/exclusion itself. Over the longer term, the benefit of being in the index is that as new money enters the market (e.g. compulsory super contributions), some of it has to find its way into index funds which adds to the buy side (and locks up some of the shares).

Short version: it's good for us but in the short term, most of the upside is already in the share price.