Before the 2000 census, the four previous censuses were considered to be of high quality; but this does not necessarily mean that there were no problems in previous censuses, and that the 2000 census was ‘useless’ as suggested by some studies (CPIRC Research Group 2003: 1; Yu and Wang 2004). A careful study may reveal the similarities in underreporting of births and young children between them and identify the specific problems in the 2000 census.
4.2.1 Age and sex reporting of population censuses
When the tabulations of the first three censuses were released to the public after the 1982 census, the good age and sex reporting in China surprised the international demographic community (see Li 1986). One researcher found that the reported number of persons by sex and single years of age from the three censuses, and the 1982 one-per-thousand survey, passed ‘a series of stringent tests of accuracy and consistency’ (Coale 1984: 1). Another comprehensive analysis of the three censuses concluded:
Analysis of reported age-sex structures from the three censuses has shown the excellent quality of age reporting, the high but plausible sex ratios, and a possible tendency to undercount men 15-25 but no other age-sex groups in the population (Banister 1987: 49).
Studies about the later 1990 and 2000 censuses also suggest that there was good age and sex reporting (CPIRC Research Group 2003; Qiao 1995; Zha, Zeng and Guo 1996). The good age reporting of women and their children makes it possible to retrospectively calculate the age-specific fertility rates.
It has been generally agreed that this accurate age reporting is attributable to the Chinese lunar calendar and traditional customs valuing the date of birth in determining lifetime important events (Caldwell et al. 1986; Coale and Banister 1994). It has also been reported that there was no obvious misreporting of sex in the censuses (Banister 1987; Banister 1994); this is closely related to the fact that all the censuses use the field enumeration approach. A detailed regional analysis on the 1990 census suggested that minor problems of sex misreporting in some provinces could be attributed to mistakes in manual data entry (Zha, Zeng and Guo 1996).
No apparent age-sex selective undercount or overcount in adult age groups was revealed, except for the abnormal sex ratio at birth in the censuses after 1982, which led to hot debate among international demographers about its actual levels and causes (e.g. Coale and Banister 1994; Gu 1992; Gu and Xu 1994; Hull 1992; Johansson and Arvidsson 1994; Zeng et al. 1993). As revealed in later censuses, although the age-sex selective undercount of younger children was confirmed, in which a few more girls than boys were found to be unreported, the retrospectively estimated SRB in previous censuses was still abnormal (see Yu et al. 2003).
4.2.2 Completeness of the census coverage
The population count is the most fundamental part of a census. Two approaches are often used to examine the census completeness: using the results from an independent post-enumeration survey; and examining survival ratio of the same cohorts from one census to the next (see Anderson 2004).
In past two decades the completeness of the census coverage has declined, as illustrated by the official under-enumeration rate. The post-enumeration survey for the 1982 census reported a net underreporting rate of only 0.15 percent (Li 1986).
The 1990 census had slightly more under-enumeration, but the post-census survey reported a net underreporting rate of only 0.6 percent (Zhang and Cui 1994). However, the 2000 census was a different story. The post-enumeration survey suggested a much higher under-enumeration rate of 1.81 percent, 30 times that in the 1990 census (SSB 2002b).
The examination of the survival ratio between two neighbouring censuses is a useful approach to the problem of undercount or overcount in censuses. Figures 4.1 and 4.2 present the single years of age distribution of the same cohorts aged 10-60 in 2000 in the 1982, 1990 and 2000 censuses. The survival ratio for 1982-90 suggests that there were slight undercounts or overcounts in both censuses, but the survival ratio for 1990-2000 indicates a possible overcount problem in the 2000 census. Certainly, caution is needed in simply interpreting this as evidence of undercount in previous censuses, as the later censuses could also overcount population. In general, two subpopulation groups were more likely to be undercounted or overcounted: children aged below 10 and adult migrants aged between 20 and 40. This pattern is similar in censuses in many other countries (Anderson 2004). But in China, it is closely associated with two important social circumstances: the family planning program and the increasingly rising population mobility.
It is very important to identify the effects from these two factors over time. The family planning program has affected the reporting of births and young children since the late 1970s. As already discussed, since the mid-1980s, the rural family planning policy has been modified and kept stable; meanwhile, as the popular fertility preferences have changed and actual fertility has declined, it is likely that there were fewer out-of-plan births, so fewer of them needed to go unreported in the 1990s. There is no strong reason to believe that the program spoiled the completeness of the census more in 2000 than in 1990, as suggested by some authors (see Goodkind 2004).
Figure 4.1Single years of age distribution of males aged 10-60 in 2000 in China in the 1982, 1990 and 2000 censuses
Figure 4.2 Single years of age distribution of females aged 10-60 in 2000 in China in the 1982, 1990 and 2000 censuses
Source: The census tabulations of the 1982, 1990 and 2000 census, SSB (1984; 1993; 2002b).
4 6 8 10 12 14 16 10 15 20 25 30 35 40 45 50 55 60 Age at mid-2000 Number (millions)
1982 Females 1990 Females 2000 Females 4 6 8 10 12 14 16 10 15 20 25 30 35 40 45 50 55 60 Age at mid-2000 Number (millions)
The rapid societal changes since the 1980s have been increasingly significant in affecting the census counting. The high quality of the 1982 census benefited from many favourable conditions, such as the then reliable hukou registrations, very low population mobility, and fewer effects from the one-child family planning campaign at its initial stage. But in the following 1990 and 2000 censuses, these favourable circumstances had greatly deteriorated. The most important impact came from the large-scale rural-urban and urban-urban population mobility during the 1990s.