Members of the graduating class of 2016 attend the Commencement ceremony of the 262nd Academic Year of Columbia University in New York, the on May 18, 2016. More than 15,000 graduates range in age from 18 to 82, including some 1800 international students from more than 100 countries participated in the ceremony here on Wednesday. (Xinhua/Li Muzi)

Members of the graduating class of 2016 attend the Commencement ceremony of the 262nd Academic Year of Columbia University in New York, the United States on May 18, 2016. More than 15,000 graduates range in age from 18 to 82, including some 1800 international students from more than 100 countries participated in the ceremony here on Wednesday. (Xinhua/Li Muzi)

Members of the graduating class of 2016 attend the Commencement ceremony of the 262nd Academic Year of Columbia University in New York, the United States on May 18, 2016. More than 15,000 graduates range in age from 18 to 82, including some 1800 international students from more than 100 countries participated in the ceremony here on Wednesday. (Xinhua/Li Muzi)

Members of the graduating class of 2016 blow bubbles during the Commencement ceremony of the 262nd Academic Year of Columbia University in New York, the United States on May 18, 2016. More than 15,000 graduates range in age from 18 to 82, including some 1800 international students from more than 100 countries participated in the ceremony here on Wednesday. (Xinhua/Li Muzi)

Lee C. Bollinger, President of Columbia University, addresses the Commencement ceremony of the 262nd Academic Year of Columbia University in New York, the United States on May 18, 2016. More than 15,000 graduates range in age from 18 to 82, including some 1800 international students from more than 100 countries participated in the ceremony here on Wednesday. (Xinhua/Li Muzi)

A graduate takes photo with her mobile phone during the Commencement ceremony of the 262nd Academic Year of Columbia University in New York, the United States on May 18, 2016. More than 15,000 graduates range in age from 18 to 82, including some 1800 international students from more than 100 countries participated in the ceremony here on Wednesday. (Xinhua/Li Muzi)

Members of the graduating class of 2016 attend the Commencement ceremony of the 262nd Academic Year of Columbia University in New York, the United States on May 18, 2016. More than 15,000 graduates range in age from 18 to 82, including some 1800 international students from more than 100 countries participated in the ceremony here on Wednesday. (Xinhua/Li Muzi)

Members of the graduating class of 2016 attend the Commencement ceremony of the 262nd Academic Year of Columbia University in New York, the United States on May 18, 2016. More than 15,000 graduates range in age from 18 to 82, including some 1800 international students from more than 100 countries participated in the ceremony here on Wednesday. (Xinhua/Li Muzi)

Secretary-General addresses the Commencement ceremony of the 262nd Academic Year of Columbia University in New York, the United States on May 18, 2016. More than 15,000 graduates range in age from 18 to 82, including some 1800 international students from more than 100 countries participated in the ceremony here on Wednesday. (Xinhua/Li Muzi)

Members of the graduating class of 2016 attend the Commencement ceremony of the 262nd Academic Year of Columbia University in New York, the United States on May 18, 2016. More than 15,000 graduates range in age from 18 to 82, including some 1800 international students from more than 100 countries participated in the ceremony here on Wednesday. (Xinhua/Li Muzi) 10

Members of the graduating class of 2016 attend the Commencement ceremony of the 262nd Academic Year of Columbia University in New York, the United States on May 18, 2016. More than 15,000 graduates range in age from 18 to 82, including some 1800 international students from more than 100 countries participated in the ceremony here on Wednesday. (Xinhua/Li Muzi) 11

A graduate posted personal messages on her hat is pictured during the Commencement ceremony of the 262nd Academic Year of Columbia University in New York, the United States on May 18, 2016. More than 15,000 graduates range in age from 18 to 82, including some 1800 international students from more than 100 countries participated in the ceremony here on Wednesday. (Xinhua/Li Muzi) 12

Chinese graduates are pictured during the Commencement ceremony of the 262nd Academic Year of Columbia University in New York, the United States on May 18, 2016. More than 15,000 graduates range in age from 18 to 82, including some 1800 international students from more than 100 countries participated in the ceremony here on Wednesday. (Xinhua/Li Muzi) 13

A graduate wearing a hat reads "Class of 2016" attends the Commencement ceremony of the 262nd Academic Year of Columbia University in New York, the United States on May 18, 2016. More than 15,000 graduates range in age from 18 to 82, including some 1800 international students from more than 100 countries participated in the ceremony here on Wednesday. (Xinhua/Li Muzi) 14

A group of Chinese graduates throw their hats into the sky after the Commencement ceremony of the 262nd Academic Year of Columbia University in New York, the United States on May 18, 2016. More than 15,000 graduates range in age from 18 to 82, including some 1800 international students from more than 100 countries participated in the ceremony here on Wednesday. (Xinhua/Li Muzi) 15