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Annual data estimates lead to gaps with census

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Commuters on a subway in Beijing during the morning rush hour on November 24, 2020. [Photo/IC]

After the release of data from the Seventh National and Provincial Census, some people might have been surprised to find that many indices, including total population, population growth, age and sex structures, and the distribution of the population among between urban and rural areas and between ethnic groups, are not consistent, or even show relatively large differences, with the annual demographic data published previously.

For example, the population of 0-14 years old in the seventh national census is 253 million, or 14 million more than the 239 million new births of the previous 15 years, between 2006 and 2020. Logically, the population of 0-14 years should have been much less than 239 million considering the premature deaths of children in this age group. It may also be surprising to see the population of 15-59 year olds in 2020 “suddenly” drop by 20 million compared to 2019.

But it is normal that the census data and the annual demographic data previously published are different. Annual demographic data published between two censuses, such as birth rate, death rate, population growth rate, total population, and age and ethnic structures, are all based on a comprehensive and scientific analysis, the calculation and estimation of vital statistics, migration registration data and sample survey data.

This is also how demographic data are primarily produced in non-census years in most other countries. Strictly speaking, demographic data published in years without a census, such as total population, population structure and growth rate, ethnic structure, are not data from a direct census, but demographic data. estimated.

In the United States, the birth rate, population growth rate and total population released each year are also estimates based on a comprehensive analysis of births and deaths from Vital Statistics System, data registration of international migration and data on the age of the population of the previous year. census.

In China, annual demographic data for non-census years is often based on sample surveys, which conduct a population survey on a 1: 1,000 basis, calculate various population indicators based on the samples, and use these statistical indicators to calculate the general population. and estimate aggregate population indicators, such as growth rate, age structure and ethnic structure.

Since this is a sample survey, which will inevitably involve sampling errors, these estimates will be close to the census data, but not in perfect agreement with them. For some indicators that require a large sample to be calculated more accurately, such as birth rate, composition of ethnic minorities, and population indicators, the differences could be larger.

For example, according to the Seventh National Census, the population of Guangdong Province is 126.01 million, 12.55 million more than the 113.46 million reported in 2018, and northeast China has a population of 98.51 million, 9.85 million less than 108.36 million announced in 2018.

It is normal that the population counts for Guangdong, northeast China, and the Xinjiang Uyghur Autonomous Region in this census do not match the previously announced annual demographics, as estimates based on sample surveys, which are generally close but not necessarily as accurate as authentic census data, may be greater or less than actual census data.

So what if the census data and the annual demographic data announced for non-census years do not match, and which should be considered accurate? Since annual data for non-census years are estimates and census data are the direct results of the survey and the universal survey, the latter are generally used by the international community as a standard, and “technology estimate of the intercensal population ”is used. verify and revise the main indicators of the annual demographic data between the two censuses, so as to make the specific data for each year consistent with the real evolution of the population.

For example, in Canada, the revision of previous data begins shortly after an agricultural census is taken. After the 2010 census, the United States also revised its demographics from 2000 to 2010 to more accurately reflect population growth and development. After the Sixth Population Census, China also used “intercensal population estimation technology” to revise the annual birth rate and population growth rate from 2000 to 2010, and released the revised results. And in statistical yearbooks published later, the revised data was used for population indices from 2000 to 2010.

The missing reporting rate from the Seventh National Census is only 0.05%, lower than in 1982 and a record for the missing reporting rate from previous censuses, making it the most accurate census since the founding of the People’s Republic of China. This was made possible due to the high quality of the census survey which revealed inconsistencies between census data and some annual data from non-census years, some discrepancies being relatively large.

After the census, the National Bureau of Statistics, on the basis of the more accurate and authoritative census data, verified and revised the data on birth rates and growth rates at the national level, giving a truer picture and more details of the growth and development of the Chinese population. .

The author is director of the Center for Population Development Studies at Renmin University of China.

Opinions do not necessarily reflect those of China Daily.


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