For the first, researchers interviewed the families of one million people who had died in 24 cities and 74 rural counties to establish if the dead person had smoked. The second study is ongoing and is looking at quarter of a million men aged over 40. It is recording the mortality and causes of death of these men over a 30-year period through annual monitoring, taking into account diet, blood pressure, drinking and other factors. Five years of the study have so far been completed, but the findings fit with those in the retrospective study - that tobacco kills half of all smokers. In older men, there was a greater danger of dying from respiratory disease.
Few women smoke in China and, unlike with men, the number is falling.
No-one knows why, but Dr Zhengming Chen of Oxford University suggested it could be due to China's recent history and social development. Causes of death Smokers who got hooked young were most likely to die prematurely. But they say this reflects past smoking habits. Ignorance Surveys showed two-thirds of Chinese people think smoking does little or no harm. Dr Zhengming said the increase in tobacco consumption did not seem to be due to promotion by tobacco companies since it had been rising since the 1970s - in much the same way as US rates rose between 1910 and 1950.