The aim of the census is to determine how many people live in Germany and how they live and work. Everyone living in the Federal Republic of Germany on 15 May 2022 was counted during the census. Following on from the 2011 census, most of the data was obtained from existing sources such as the population data stored in public administration registers. This method is known as a “register-based census”. However, the number of inhabitants cannot be calculated by simply counting the people recorded in population registers, because not all information contained in the population registers are accurate and up-to-date.

In order to update the population registers, each German municipality expects the local residents to report any changes in good time. However, this is not always the case. Some people are not registered at their place of residence, while others are in the register but have since moved house or passed away. A person who exists in the population register but no longer lives at the address recorded there is referred to as a “nominal record”. A person who lives at a certain address but is not recorded there in the population register is referred to as a “missing record”.

For this reason, and based on the observations made during the 2011 census, a number of additional measures were planned during the 2022 census to correct the population register count in the statistics. Firstly, the register data is cleaned up by means of a multiple case check (1) and secondly, the register data undergoes various “primary statistical adjustments” (2).

1. Multiple case check

The population registers in towns, cities and municipalities were first consulted to determine the official population. For this purpose, the towns, cities and municipalities provided their local statistical office with the records of all persons registered with them by the scheduled census date: 15 May 2022. These records were resubmitted three months later to take into account any registrations and de-registrations that took place before the census date but were only entered in the population register afterwards.

The data submissions were collated by the Statistical Offices of the Federation and the Länder under the most stringent data protection requirements. The data from all municipalities had to be collated to create one database, because population registers are generally managed locally. In other words, each municipality is responsible for maintaining and updating its own population registers. This is usually done by the residents’ registration office in each municipality.

As each population register is managed locally, some people may be registered at several addresses or only at a secondary place of residence. A “multiple case check” was carried out to uncover such erroneous entries and make the necessary adjustments to the population count. Each person was then only included once in the national population count with one single place of residence (or one main place of residence and other secondary places of residence).

2. Primary statistical adjustments

In addition, some of the population were interviewed directly to adjust the data obtained from the population registers. This is known as a “primary statistical survey”. When it comes to determining the population in the 2022 census, the primary statistical parts include a) a survey of randomly selected households and b) a full survey of dormitories and shared accommodation.

Once the surveys had been conducted, the statistical offices compared the results with the population count. The surveys of households, dormitories and shared accommodation were conducted for the purpose of identifying any register errors (over-coverage, under-coverage, nominal records and missing records) and to correct them in the statistics. The missing records detected during the full survey of dormitories and shared accommodation – and those extrapolated from the household survey – were added to the population count and the nominal records will be deducted. This is how the number of inhabitants was calculated for each municipality.

It is important to note that these measures were only intended to correct the population figures. The municipalities were only informed of how many persons were correctly registered and how many over-coverage and under-coverage was contained in their registers. If, for example, the census showed that a person lives in a municipality without being registered there, that person’s name must not be passed on to the municipality under any circumstances. This is governed by the so-called “prohibition on feedback”.

a) Survey of randomly selected households

During the household survey, only part of the population was interviewed. A sample of addresses was taken and the result was then extrapolated for the entire population. A complex mathematical formula was used to randomly select the addresses. All persons living at a sample address on the survey date were identified and interviewed. The survey offices in the towns, cities and municipalities submited the results to their local statistical office.

In the 2022 census, the survey of randomly selected households was used for the first time to adjust the information obtained from the population registers in all municipalities, in order to generate the definitive figures for the statistics. In the 2011 census, this was limited to municipalities with at least 10,000 inhabitants and an alternative method was used to adjust the figures in smaller municipalities. By expanding the sample to all municipalities in the 2022 census, a uniform method could be used to determine the number of inhabitants, regardless of the size of each municipality.

The sample sizes had to be large enough to enable the number of inhabitants to be determined with sufficient accuracy. This is naturally the case in large municipalities, but a large percentage of the population had to be included in the sample in smaller municipalities. A full survey was therefore required in some municipalities, which meant that all people living there were interviewed. However, the sample may also have been drawn from municipal associations or parts of municipal associations instead of individual municipalities. That may have reduced the number of respondents in those areas.

b) Full survey of residential establishments and collective living quarters

An above-average amount of outdated and/or incomplete information can be assumed for residential establishments and collective living quarters due to relatively frequent change of residents and inadequate reporting. In view of this problem, a full survey took place at those addresses. In other words, information was collected on all residents and the data did not have to be extrapolated.