S&P Dow Jones Indices announced the September ASX 200 rebalance on September 4, with changes effective before trading opens on September 21. Elsight and Smartgroup are among the additions named in the release. An index change can affect which shares tracking funds need to hold, but it does not itself increase a company's sales or improve its balance sheet.
The trading deadline and the announcement are different
A rebalance changes the membership or weights used by an index. Tracking funds then manage their portfolios around that benchmark and their own implementation methods. Some market participants anticipate the change well before its effective date. Buying after an inclusion headline therefore does not guarantee that any associated demand still lies ahead.
Weight matters more than the headline count
If a hypothetical A$100 million fund needs a 0.2% allocation to a company, the target exposure is A$200,000. That illustration is not an announced weight for either new constituent. Fund size, index weight, existing holdings and tracking choices determine the actual adjustment, and different products may follow different ASX indices.
Check the exact benchmark in your ETF's documents and compare price performance with dividends handled consistently. For an individual share, return to earnings, cash generation and valuation after considering index flows. September 21 is a mechanical milestone; the company's long-term return still depends on business performance and the price paid.