Elon Musk has spent $2.64 billion on Twitter stock this year, snapping up shares almost everyday since January

• Elon Musk has been buying Twitter stock on an almost daily basis since January, an SEC filing shows.
• The billionaire currently owns over 73 million shares, or about 9.1% of the social media company.

Elon Musk has been buying Twitter stock nearly everyday since January, spending $2.64 billion for his stake in the company, a Tuesday SEC filing revealed.

The filing said Musk owns 73.1 million shares, or about 9.1% of the company. At Monday's closing bell, his stake was worth roughly $3.73 billion. Twitter stock has skyrocketed more than 25% since Musk's position became public.

On Monday, Musk's ownership stake had been disclosed via a 13G filing, which indicates a passive stake, or when a shareholder doesn't try to exert influence. The new 13D filing, instead, confirms that the Tesla chief will be an active investor who looks to hold sway over Twitter's business and operations.

Twitter CEO Parag Argrawal announced that the company would be appointing Musk as a board member, signaling his status as an active investor.

Despite Twitter's massive stock rally, analysts at Bernstein said the market was overreacting, driven by speculation that the social media giant could be sold.

"The investor reaction to the news seems a bit extreme to us," the analysts wrote. "We believe the fundamentals and challenges with Twitter remain broadly the same."

Bernstein also speculated that Musk's appointment could ease some of Twitter's guidelines on censorship and free speech, as the billionaire earlier highlighted pitfalls of the platform.

On March 25, Musk polled his more than 80 million followers, asking whether Twitter abides by free speech principles. On March 28, he tweeted that he was considering building his own social media platform.

His interest in Twitter is "mainly personal," Bernstein analysts said, given his fervor for the topic of free speech, among other reasons.

"Big Short" investor Michael Burry, meanwhile, seemed to welcome Musk's appointment to Twitter's brass, writing in a now-deleted tweet that the move is "good for America."