He joined the Social Sciences Research Centre of the University of Hong Kong when it was established in 1987. In 1991, he set up the POP within the centre and began to study the development of public opinion in Hong Kong. To match the development of the university, Dr. Chung and his POP team was transferred to the Journalism and Media Studies Centre at the university on 1 May, 2000, and then back to the Faculty of Social Sciences on 1 January, 2002.
The programme regularly conducts independent surveys, covers media development, and launches electoral studies, policy issues, and youth studies. Under his leadership, the propgramme is famous for being impartial and professional, and is a highly respected public opinion study programme in the region. Its studies are widely covered in mass media and frequently cited in academic publications.
Dr Chung has written numerous articles on public opinion and social surveys published in various journals and periodicals, and is the Chief Editor of the monthly POP newsletters, POP Express, and the HKU POP Site.
Besides, Dr Chung is a Panelist of Television Programme Advisory Panel of Radio Television Hong Kong (RTHK) and a Panelist of the Television Programme Appreciation Index Research Panel. From 1993 to 1994, Dr Chung served as a part-time community panelist of the Central Policy Unit of the Hong Kong Government. He then became a part-time member of the Central Policy Unit between 1994 and 1999. Between 1997 and 2003, he served as a member of the Community Research Sub-committee of the Citizens Advisory Committee on Community Relations of the Independent Commission Against Corruption (ICAC), and between 1998 and 2003, as a member of the Citizens Advisory Committee on Community Relations.
Internationally, he has been the Hong Kong representative at the World Association for Public Opinion Research (WAPOR) for a number of years. From 2006 to 2008, Dr Chung was the elected Secretary-Treasurer of WAPOR. He is also a member of the Editorial Board of the International Journal of Public Opinion Research.
Although the allegations were denied by Tung and HKU, a controversy erupted over the question of political interference in academic freedom. HKU set up a three-member panel led by Justice Noel Power to investigate Chung's claims. After 11 days of open hearings in August, the panel concluded that there were what it called "covert attempts" to pressure Chung into discontinuing his polls. The panel concluded that Dr. Chung is "an honest witness who was telling the truth in relation to the matters he is complaining about", but "neither Lo [The Chief Executive's Senior Special Assistant] nor the vice chancellor disclosed the full and truthful extent of what was said in [the] meetings". The saga ended with the resignation of the Vice-Chancellor and Pro-Vice Chancellor of the University of Hong Kong - Prof. Cheng Yiu-chung and Prof. Wong Siu-lun just before the University Council met on September 9 to vote on whether or not to accept the panel's report. At the end, Dr Chung's Public Opinion Programme continues to function and is growing from strength to strength in the years subsequent to that crisis, and becoming arguably the most authoritative source of public opinion information and assessment in Hong Kong.
In addition to sports, astronomy is also Dr. Chung's interest.