Activision Blizzard Inc. said that its two-for-one stock split is effective and its common stock began trading Monday on a split-adjusted basis.

As a result of the stock split, there are approximately 1.3 billion shares of Santa Monica-based Activision Blizzard’s common stock issued and outstanding.

Vivendi SA completed the merger of its video game business with Activision Inc. in July and now owns more than 54 percent of the combined companies.

Activision shares were down 24 cents, or 1 percent, to $16.63 in morning trading on the Nasdaq.