Some large high-speed trading firms are teaming up with options-exchange operator Miami International Holdings to create next year what could be the 15th U.S. stock exchange.

Some large high-speed trading firms are teaming up with options-exchange operator Miami International Holdings Inc. to create next year what could be the 15th U.S. stock exchange.

The deal, announced by Miami International on Friday, comes just one week after the 14th stock exchange won regulatory approval. The proliferation of new equities-trading platforms could fuel longstanding complaints by brokers that the stock market is overly complex and fragmented between too many exchanges.

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