context: The University of Chicago also maintains facilities apart from its main campus. The university's Booth School of Business maintains campuses in Singapore, London, and the downtown Streeterville neighborhood of Chicago. The Center in Paris, a campus located on the left bank of the Seine in Paris, hosts various undergraduate and graduate study programs. In fall 2010, the University of Chicago also opened a center in Beijing, near Renmin University's campus in Haidian District. The most recent additions are a center in New Delhi, India, which opened in 2014, and a center in Hong Kong which opened in 2015.
question: In what year were the oldest additions in Hong Kong opened?