Baidu shares fell on Wednesday, after chief scientist Andrew Ng announced he is leaving the company less than three years after joining. Ng announced his departure in a post on Medium late Tuesday. Baidu shares were down more than 1½ percent in market hours, trading around 168.51. Ng had joined the company in 2014 to help help develop new businesses around artificial intelligence and machine learning, areas Baidu has previously identified as a major strategic focus. Baidu told the Financial Times it will not hire a direct replacement, but instead move Ng's teams into the AI Group, which will be headed by current vice president Haifeng Wang.