The stock index on which today's new futures products are based, the Hang Seng 100, was launched on April 20 by Hang Seng Bank subsidiary HSI Services. The Hang Seng 100, which was launched alongside the New Hang Seng MidCap 50 Index, gives investors a performance gauge for middle to bigger listed companies. It is based on the biggest 100 listed companies in Hong Kong. These companies are chosen by selecting the stocks with the highest market capitalisation over a 12-month average and those with the highest aggregate turnover over 24 months. As at April 30, the stocks in the Hang Seng 100 had accounted for 82.8 per cent of total market capitalisation in the previous 12 months and for 76.1 per cent of turnover over the 24 months. These numbers show the index is more representative than the Hang Seng Index whose stocks accounted for just 70 per cent of capitalisation and 47 per cent of turnover during the same periods. Anthony Wong, chairman of HSI Services, said: 'We believe that the Hang Seng family of indexes, which will include seven indexes in total after the launch of these two indexes, will meet the different needs of investors.' Mr Wong believed the Hang Seng Index, made up of 33 major stocks, would still be the benchmark of the Hong Kong stock market. 'The Hang Seng 100 and the New Hang Seng MidCap 50 Index will form an index series providing alternative broader-based stock market indicators to the Hang Seng Index,' he said. The Hang Seng China-Affiliated Corporations Index and the Hang Seng China Enterprises Index would continue to track the movement of the market related to the mainland sector, he said. To qualify as a constituent of the Hang Seng 100, a company must not be 'foreign' under the definition used by the stock exchange and may not have been dormant for more than 20 trading days in the past 12 months.