China's been celebrating the 40th anniversary of reform and opening up. In a recent gathering, President Xi Jinping summed up in a speech the great achievement of the Chinese people in the past four decades. With that in mind, CGTN's Tian Wei talked to one of the well-respected voices in the US, Professor Stephen Roach from Yale University. Having observed China's development for over 30 years, Professor Roach shared his thoughts about what China needs to do next.