The drop in Bezos' stake was reported in the Friday filing, under her ex-husband and Amazon CEO Jeff Bezos' name. Jeff Bezos retains sole voting control of MacKenzie Bezos' stake, which now stands at 19.5 million shares, or about 200,000 fewer shares than the 19.7 million she received as part of their divorce.
Last May, MacKenzie Bezos signed the Giving Pledge, which was started by Warren Buffett and Bill and Melinda Gates in 2010. As part of the move, she pledged to give away half of her wealth to charitable causes.
Jeff Bezos has yet to sign the pledge, but applauded his ex-wife's decision.