Nasdaq has lost ground in its battle for market share in trading of stocks listed on its own exchange, as a rival system set up less than two years ago boosted its slice to 7.4%.

The exchange's September market share in its own stocks was down 1.6% on the same month last year and August this year. Its share of the total US equities market fell 1.7% in September, compared to the previous month, but rose by half a percentage point compared to September last year.