THE stock exchange has published for the first time the market shares of its members, which show small brokers losing out gradually to their larger competitors. The report was based on monthly transaction levy payments. The exchange classifies brokers under three categories or constituencies. Constituency A comprises 14 members which make the largest transaction levy payments, while B has 51 members and C, the rest of the members. While the market share started as a 35:30:35 split among the three groups in mid-1992, the balance tilted in favour of the smaller brokers in early 1993, with June as the peak period. Last year, the market share of group C declined consistently, a trend that continued until this year with the share reaching about 29 per cent. A low of 25 per cent was set in January. On the other hand, the big players secured as high as 45 per cent in April. 'In 1993, there was active turnover in the second-tier and third-tier stocks which generated a lot of business for the small brokers,' said Teresa Wong, vice-chairman of the Hong Kong Securities Professionals Alumni Association. The reversal of fortunes experienced by these punters after 1993 sent a sharp fall in turnover on these stocks. 'Instead, investors turn to the blue chips or index-related stocks,' she said. As a result, the bigger brokers benefited because they tended to concentrate trading in blue chips. While there was shift of market share between the A and C groups, the B group's share remained steady. This is because the group consists of the bigger ones which cannot get into the first group and the smaller ones. 'The change in the turnover of these two groups balanced each other out,' Ms Wong said. Disclosing market share information would enhance transparency, she said. But it would also put pressure on the management of the brokerages.