The Tokyo Stock Exchange said Thursday it will change the method of calculating the Topix index of all first section issues to better track corporate performances.
The TSE said the new calculation method will be based on floating shares that could be traded more actively than cross-held shares.
Cross-held shares are among those used for calculating the index.
The TSE said it will announce details of the new method and a timetable for its introduction by late June.
The TSE is likely to start introducing the new method in 2005 and fully shift to it by spring 2006, TSE officials said.