The S&P/ASX 200 index (also known as the XJO) is the main benchmark for the Australian equity market (replacing the venerable All Ords as the industry standard).

The index is made up of 200 of the top stocks, which boast a total value of around $1.1 billion (end of March 2010).

While there are around 2000 stocks listed on the ASX, these top 200 stocks make up almost 80% of the total value of the market.

The XJO provides investors and fund managers with a benchmark, a level of performance to compare their own Australian share trading to.

The index also forms the basis for futures contracts such as the Share Price Index (SPI).

Piece of the pie

The index is weighted by the float-adjusted market capitalisation of each stock, which means a 1% move in one of the bigger companies, moves the index more than a 1% move in a smaller company.

The finance sector makes up around a third of the index (by market cap, not number of companies), mostly through the big four banks.

Around 25% of the index is made up by mining stocks, and BHP, the market’s biggest stock, accounts for around 12-13% of the index just on its own.

Wild ride

Started up on 31 March, 200, the XJO began with a value of 3133, which was the value of the All Ordinaries at the time, and there has been plenty of action since then.

The XJO hit a low of 2693 in March 2003, just before the start of a bull market.

Over the next four and a half years, the XJO rose by over 150%, hitting a high of 6852 in November 2007.

This is when the global financial crisis (GFC) kicked in, sending the XJO spiraling lower over the next 18 months.

After hitting a GFC low of 3120 in March 2009, the XJO rose by around 50% over the next 12 months.

This party is invite only

To be eligible for inclusion in the ASX 200 index, a stock must meet market capitalisation, liquidity and listing criteria.

Market capitalisation is determined using a function of current index shares, the latest stock price and the investable weight factor (known as IWF).

IWF is negatively impacted by strategic holdings that are corporate, private or government in nature, meaning shares owned by founders, directors of the company and other companies are excluded.

The liquidity requirement for inclusion in the ASX 200 is that the trading volume (in dollar value terms) and the number of stock transactions must be higher than 0.025% of the total trading volume of all eligible securities.

Lastly – and this goes without saying – a company can only be listed on the ASX 200 if it is listed on the Australian Stock Exchange (ASX).

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