Nasdaq OMX Group’s two option trading venues together handled more volume than rival markets for the third straight month, figures from the Options Clearing Corp. showed on Wednesday.

The exchange operator, which runs Nasdaq PHLX and the smaller NOM platform, said it captured a record 28.68 percent market share for all U.S. stock and stock-index option trades in November.

But some of Nasdaq’s market share on its PHLX venue, formerly known as the Philadelphia Stock Exchange, comes from a specialized trading strategy linked to bets on stock dividends.

Nasdaq has defended these so-called dividend trades in the past, saying they are legitimate. [ID:nN03167568].

The International Securities Exchange, owned by Deutsche Boerse’s (DB1Gn.DE) futures exchange Eurex, repeated its view that these trades temporarily inflate and distort trading volume and market share when transacted.

Dividend trades accounted for 26 percent of the 82.9 million contracts of total equity options volume traded on the PHLX in November, ISE estimates released on Wednesday showed.

CBOE Holdings Inc (CBOE.O), which operates CBOE and the electronic C2 options platform, attracted the second biggest share of option trading last month, handling 26.6 percent.

The Chicago Board Options Exchange’s market share was also distorted by the inclusion in overall industry figures of the dividend trades.

Excluding the dividend trades, CBOE’s market share for November would be 27.7 percent, not the 26.3 percent it reported, CBOE Holdings said in a statement.

CBOE’s alternative C2 platform traded nearly 1.2 million contracts for the first full month of trading since its launch on Oct. 29, CBOE Holdings said. C2’s total market share in November was 0.33 percent.

NYSE Euronext (NYX.N), which runs the Amex and NYSE Arca options trading venues, handled 23.09 percent.