How is the world's population growth controlled

Population development

Herwig Birg

To person

Prof. Dr. rer. pole. habil. From 1981 to 2004, Herwig Birg was head of the chair for population science and managing director of the Institute for Population Research and Social Policy (IBS) at Bielefeld University. His main research areas are population theory, fertility theory, migration theory, mortality analysis and life expectancy, population forecast and simulation models, and population projections. Contact: »[email protected]« Homepage: »«

After centuries of unhurried growth, world population growth accelerated in the 20th century. But since 1965-1970 at the latest, a trend reversal has been discernible, the pioneers of which are the industrialized countries. Dealing with the influence of this development on the functionality of the social security system is one of the challenges of the present.

Hundreds of cars are stuck in a traffic jam. (& copy AP)


Population is more than a mere collection of people. It is defined by the characteristics common to individuals, for example residence and place of work, and also by the social, economic and cultural relationships between people.

The population of every country, region and municipality is subject to constant change. This happens through births and deaths as well as immigration and emigration to other areas of the same country (internal migration) or to foreign countries (external migration). Of these four causes of change, the first - the number of births - is by far the most important, because the other three depend on it in an elementary way: Every birth leads to a death at some point and usually to several changes of residence in the life cycle, which in the Population statistics appear as immigration and emigration. The sum of all four components for a given year or any other period is either positive (in the case of population growth), negative (population shrinkage), or zero (population stagnation).

The changes in the population or birth balance are not only important for society as a whole, but also - indirectly - for the individual. Because individual decisions, such as those for or against children, not only change society as a whole, but also affect the individual. It may be the case that if the birth rate continues to be low for society as a whole, a shrinking number of employees paying into pension or health insurance is confronted with a simultaneous absolute increase in the number of elderly people to be cared for and as a result pensions must be reduced or health insurance contributions increased.

The social effects of the demographic development can lead to the fact that the individual decisions that are optimal from the point of view of the individual bring about a demographic and economic state of society in their entirety, through which the standard of living for the individual is reduced, although or precisely because the individuals in each case for have made optimal decisions.

In the German public, these relationships are continuously discussed out of concern. They are not actually new, but have historical forerunners. The figures on the population development of the world in the past centuries are based on decades of international research on the basis of diverse historical and literary sources. Regular censuses as a basis for demographic information have been available - apart from forerunners, for example in the Roman Empire - for few European countries only since the 18th century.

Most developing countries still do not have reliable population data. For example, annual births and deaths between censuses every ten years or so are still not fully recorded in many countries, and so is immigration and emigration across national borders and intra-country movements.

Germany has had no precise information on the number and composition of its population for more than 20 years. The last census took place in the former Federal Republic in 1987 and in the former GDR in 1981. In 2011 (cut-off date May 9, 2011) the microcensus, a new type of census, will be carried out in which only ten percent of households are surveyed in a sample instead of all residents as before. These figures are supplemented by information from various registers. The first results for the number of inhabitants are expected to be available in autumn 2012, and results for households in spring 2013.

In the years between the censuses, the population is calculated using the number of births and deaths and immigration and emigration by adding up the births and immigration each year and subtracting the deaths and emigration (population forecast). The number of births and deaths shows practically no errors, unlike the number of immigration and emigration from abroad, which is of the same order of magnitude as births and deaths. Since the people moving abroad do not all deregister at the registration offices and the illegal immigrants do not register, the population figures of the official statistics are affected by two errors with opposite signs, the exact extent of which is naturally unknown. Estimates of the number of unregistered residents living in Germany vary between 500,000 and over a million. It is assumed that, due to the incomplete registered emigration since 1987, there are around 1.3 million fewer people living in the Federal Republic than indicated in the official population statistics.

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Census - How states count their peoples

The Indian Minister of the Interior called the "largest project since the creation of mankind" the census of all residents, which began in April [2010]. Since then, 2.5 million employees are in the process of statistically recording each of the more than 1.1 billion Indians. Anyone over the age of 15 must give a fingerprint and be photographed. The count will probably last until next spring [2011].

It only took ten days in China. A nationwide survey began there on November 1, 2010, to which 6.5 million censuses flocked. Since up to 200 million of the estimated 1.3 billion Chinese are said to be migrant workers, who sometimes live illegally, the counters repeatedly faced a problem: In many apartments there was unsatisfactory information and apparently more residents than rooms. So the census takers evaded evidence - and counted the toothbrushes that were available.
In the United States, a country with no residents' registration offices, the census is of key importance. The American United States Census took place last spring [2010] for the 23rd time (every ten years since 1790). The data collected are used to tailor constituencies and to calculate public payments: the more residents are counted, the more municipalities receive the more money - an important reason for the good image of the census. This year, however, the high costs of the census were criticized.
In the neighboring country of Canada, in June [2010] the government replaced the comprehensive mandatory survey of a fifth of the population ("a waste of money"). These 20 percent had previously received a longer questionnaire than their fellow citizens. In the future, participation in this long form questionnaire should be voluntary - but still reach 30 percent of the population. The bottom line is that critics fear higher costs: They point out that, under the constant fire of telephone surveys and advertising disguised as such, citizens are getting tired of answering.
Good experiences have been made in Switzerland, where the official statisticians also compile the building cadastre. This practical benefit increases acceptance - but mixes administration and statistics with one another. The European Union requires its member states to provide a fixed set of population data every ten years, but does not specify any specific methodology: both reference dates and the type of survey are set nationally.
In Great Britain there is currently a discussion as to whether the 2011 census should be the last one based on questionnaires. A pure analysis of official registers could replace it. In the 1990s, the Netherlands, Denmark and Sweden had already started such a cadastral evaluation. However, every citizen in Scandinavia has a unique identification number under which he is clearly and uniformly recorded in official databases from birth to death - which leads to meaningful data for statisticians.
The approach in Turkey is rigorous: there is a curfew on the census date to make the interviewers' work easier.

STX, "This is how the others count", in: Die Zeit No. 46 of November 11, 2010