From large multinationals to small growth companies, Australia's stock market indices cover different facets of the Australian economy, including natural resources, new technologies and finance. The S&P/ASX 200 is the benchmark index for the Australian stock market. It is calculated on the basis of the 200 largest companies listed on the Australian Securities Exchange (ASX) in terms of market capitalisation. Older and more comprehensive, the All Ordinaries stock market index covers around 500 of the largest companies listed on the ASX. But some Australian stock market indices are more selective; the S&P/ASX 300, the S&P/ASX 100 and the S&P/ASX 50, for example, have selections of 300, 100 and 50 stocks respectively. In addition to stock market indices constructed on the basis of the size of the market capitalisations of the companies making them up (such as the ASX MidCap 50 or the ASX Small Ordinaries, which focus on mid caps and small caps respectively), other stock market indices are constructed on the basis of specific economic sectors (such as the ASX Technology Index, the ASX 200 Resources and the ASX 200 Financials-X-A-REIT targeting the technology, natural resources and securities investment fund sectors respectively). Finally, other stock indices such as the ASX 200 VIX measure expected volatility in the Australian equity market based on options indexed to the S&P/ASX 200.