China has, in many ways, changed dramatically since the Tiananmen crackdown 21 years ago today. The Communist Party leadership reacted to the convulsions of 1989 by choosing the path of economic development and opening up to the world, while maintaining firm political control. This strategy has succeeded in making the country more stable, prosperous and confident. Millions now enjoy a standard of living previous generations could only dream of. For these reasons, the party enjoys widespread support. But many of the issues which led to the demonstrations in Tiananmen Square and elsewhere remain concerns today. The protesters in 1989 were motivated by a range of issues. They included corruption, inflation, calls for a free press and a general desire for a more liberal political system. This conflation of demands and anxieties prompted spontaneous demonstrations, which ultimately led to catastrophe when the PLA was sent in to crush the protests.

While similar mass demonstrations have not materialised on the mainland again - and the government has more sophisticated means of preventing them - many signs are emerging of discontent and unrest. Corruption, despite the government's attempts to rein it in, remains rife and sometimes sparks violence. Health scandals, such as the contamination of baby milk with melamine in 2008, cause a deep sense of grievance among victims. Industrial action by factory workers seeking better working conditions has been seen in recent weeks and pollution continues to take its toll.

The central government is well aware of the need to resolve people's problems. This can be seen, for example, in its swift reaction to the Sichuan earthquake in 2008. But the system still lacks a safety valve. Without rule of law, independent courts, media freedom or other means through which the public can easily raise matters of concern, it remains difficult for grievances to be tackled and disputes settled smoothly. As we reflect on the Tiananmen crackdown and all that has happened since, it is clear this is one of the biggest challenges facing the central government.