The ASX 200 is a float-adjusted index, which means that only fully paid-up shares are included.
The ASX 200 has some of the same constituents as the S&P/ASX 50. However, there are differences. For example, BHP is excluded from the index because it prefers to manage its businesses as separate and distinct units without reference to their market weightings (see related companies). Also excluded were Fortescue Metals Group and RFG, which were once part of the index but were excluded due to their delisting from the ASX. Other noteworthy exclusions include AGL Energy, Aristocrat Leisure, and ResMed.
The most recent additions are Glencore at #140 (13 August 2010) and Suncorp Group at #201 (15 January 2009).
How is the index calculated?
The index is calculated in real-time and published every minute when the market is open. The base value of the index was 500 points, as of 29 September 1985. The index reached an all-time high of 5408.87 on 21 December 2007, under the leadership of former chairman Mark Johnson. On 16 January 2008, the index closed above the 5000 point barrier for the first time since 26 September 2007. On 29 December 2008, the index rose through 6000 points to reach a new high of 6034.31 on heavy trading and speculation that better-than-expected fourth-quarter results would be announced after the Christmas break. The previous largest one-day loss (in points) occurred on 9 September 2008.
As of 4 February 2011, the index closed at 4022.02, off 1.9% from the previous trading day’s close of 4110.50 after a downgrade by Standard & Poor’s and a credit rating agency warning from Moody’s Investors Service about a possible negative outlook for Australian banks sparked a sell-off of financial-sector stocks.
The Australian index has been embraced by several local brokers who offer indexes on their website and published data and charts to reflect the price movement. Each index is different and each may move differently relative to its specific base day or index starting point. Some of these brokers include:
The index occasionally has a negative number. This is usually the result of a stock paying a cash dividend, which reduces its price and weighting in the index. An example would be CSL Ltd on 28 June 2017, when it reported an unfranked fully franked final dividend of A$2.48 per share, payable on 25 July 2017. The company’s shares were then downgraded from A- (excellent) to B+ (good) by Standard and Poor’s Global Ratings, resulting in the CSL Index decreasing 0.326 points (-1%) on 28 June 2017.
Another reason is due to companies with multiple classes of shares on issue. For example, AGL Energy has a separate class of shares listed on the ASX which pay no dividends and have no voting rights. This results in a disproportionally high weighting for each share as they don’t contribute to the overall index performance.