The CLHLS project covers 22 provinces:
- North (4): Beijing, Tianjian, Hebei, Shanxi;
- Northeast (3): , Liaoning, Jilin, Heilongjiang;
- East (7): Shanghai, Jiangsu, Zhejiang, Anhui, Fujian, Jiangxi, Shandong;
- Central/South (5): Henan, Hubei, Hunan, Guangdong, Guangxi;
- West (3): Chongqing, Sichuan, Shaanxi.
The exclusion of 9 provinces in the North-West parts of China where ethnic minorities share a very high proportion of population is based on previous empirical findings that show relative inaccuracy of age-reporting among elders of the minority groups in these nine provinces. Coale and Li (1991) have shown that, among the Han Chinese (and some minorities who have been culturally and residentially integrated with the Han over the years) older generations tend to use the Chinese lunar calendar, while the younger generations tend to use the Western calendar plus animal year to remember their birthdays. This is important for Han Chinese people because the precise date of birth is significant in making decisions on important life events such as matchmaking for marriage, date of marriage, and the date to start building a house, among other events. Therefore, Han Chinese, even if illiterate, can usually provide a reliable date of birth for themselves or for their close family members (Coale and Li 1991).
One the other hand, most ethnic minorities do not have such a tradition, which may lead them to exaggerate their age among old people. For example, Coale and Li (1991) found that age reporting among some ethnic minorities, especially the Uyghur ethnicity in the Xinjiang autonomous region, was seriously biased with age exaggeration, leading to abnormal age patterns of mortality at old ages for China as a whole. Once the Xinjiang data were excluded, the Chinese age pattern of mortality at old ages became rather normal as compared to other countries with accurate age reporting. They also fund evidence of likely age exaggerations in other 8 provinces than Xinjiang, where the minority groups consist of a large proportion of the total population.
Our empirical studies have confirmed the relative accuracy of age reporting among Han Chinese. Please see details in Coale and Li (1991), Wang et al. (1998), Zeng et al. (2001), and Zeng and Gu (in press).
- Coale, A.J., and S. Li (1991), The effect of age misreporting in China on the calculation of mortality rates at very high ages. Demography 28(2), pp. 293-301.
- Wang, Z., Y. Zeng, B. Jeune, and J.W. Vaupel (1998), Age validation of Han Chinese centenarians. GENUS – An International Journal of Demography 54, 123-141.
- Zeng, Y., D. Gu. (2008) Reliability of age reporting among the Chinese oldest-old in the CLHLS datasets. In Y. Zeng, D.L. Poston, D.A. Vlosky, and D. Gu. (eds.). Healthy Longevity in China:Demographic, Socioeconomic, and Psychological Dimensions. Pp 61-79. Dordrecht, The Netherlands: Springer Publisher.
- Zeng, Y., J.W. Vaupel, Z. Xiao, C. Zhang, and Y. Liu (2001), The healthy longevity survey and the active life expectancy of the oldest old in China. Population: An English selection 13 (1), pp.95-116.