Migration flows Methods

1. General information

How are migration statistics produced?

Migration statistics are based on a complete count and cover all registered arrivals and departures across municipal or federal borders involving a transfer of the main or sole residence. Their statistical unit is the migration move, not the migrant person. Generally, the number of migration moves is higher than that of migrant persons because a person may move more than once within a year.

Which migration moves are included in the statistics?

Migration statistics cover all registrations, deregistrations and change in housing status recorded by the local registration authorities in accordance with the federal law on registration. An exemption of the obligation to register exists for persons moving to a residence for less than 6 months when they have another registered residence in Germany and for persons moving from abroad for less than 3 months. These cases are consequently not included in the statistics. The obligation to register applies for refugees and asylum seekers, which are included in the migration statistics. It is however not possible to display them separately as immigration motive or immigration status are not part of the statistics.

How are migration moves presented?

Migration statistics show not only the number of arrivals and departures but also the difference between arrivals and departures in the form of net migration. Positive net migration means that more people moved in than out, which is net immigration. Negative net migration means net emigration. The volume of migration is the total of arrivals and departures between two given points in time.

In the publications, a distinction is made between internal, external and total migration. In federal statistics, internal migration covers migration moves between municipalities of a Land and migration moves between Länder. Net internal migration for the whole of Germany is always zero because departures and arrivals within Germany offset each other. In some reference years, however, net migration is not quite balanced, which is due to differences in data processing status between the Land of origin and the Land of destination.

External migration statistics cover arrivals and departures across the borders of Germany (or across the borders of the former territory of the Federal Republic). Total migration consists of internal migration and external migration.

Migration moves can be represented as migration flows at various geographical-administrative levels. The territory of origin and the territory of destination are defined and for each of them, individual areas or a regional level can be chosen. Here are examples where individual areas have been selected:

• arrivals from Land A to Land B
• arrivals from country X to Land A
• departures from Land A to country X

Where regional levels are examined, migration moves are categorised by border crossed (municipality, administrative district, administrative region, Land or Germany). Here are examples of migration flows shown in migration statistics:

• across Land border (territory of origin)
• across Land border (territory of origin) to another Land (territory of destination)
• across federal border (territory of origin) to another country (territory of destination)
• etc.

2. Key figures of migration statistics – migration rate

The migration rate reflects - for a reference year and a given territory - the migration moves per 1,000 people of the average population of that territory. It is well suited for comparisons over time and regional comparisons as it takes account of the size of the reference population.

Migration rates may by classified by age, sex or citizenship and can be calculated for subpopulations. As some groups (foreign population, young adults) often have higher mobility, it may be useful to perform studies on the mobility behaviour of different groups or on their impact on the population structure.

3. Distinguishing between citizenship and country of origin

The “country of origin” variable used in migration statistics is often confused with the “citizenship” variable. The two variables are not identical. Citizenship means that a person legally belongs to a specific state and is indicated in the passport. The country of origin refers to the country in which the person last lived. For example, someone with Polish citizenship who last lived in France and now registers in Germany has “Poland” as value for the variable "citizenship" and “France” as value for "country of origin".

4. Administrative deregistration and “deregistration with new residence unknown”

People moving out of a residence without taking a new residence in Germany are obliged to deregister. In many cases, however, people move out without deregistering. If a registration office discovers that a person no longer lives at the address she is registered at, it may perform an administrative deregistration. Administrative deregistrations are generally included in the external migration statistics.

If the registration office does not know where a person has moved to (for example, because a voter’s notification cannot be delivered), a “deregistration with new residence unknown” is carried out. For foreigners, the country of citizenship is in this case generally entered as territory of destination. Where this is not meaningful (for refugees for example), and where Germans are concerned, the value “no data provided” is entered in the variable territory of destination.

Since reference year 2015, tables on external emigration have been available separately by type of deregistration (regular or administrative deregistration).

5. Reference periods – monthly and annual results

The results of migration statistics are processed and published both monthly and annually. Since reference year 2016, the total of the reference months have formed a provisional annual result for the reference year, which differs from the final result for the reference year due to methodological reasons. The reason for the differences is that registration offices sometimes correct their previous information on migration moves; such corrections are then integrated into the annual result.

6. European migration statistics

European migration statistics based on EC Regulation 862/2007 are not comparable with the results of national migration statistics. German migration statistics cover migration moves irrespective of any minimum duration of stay, while European migration statistics include only persons who moved their usual residence for at least 12 months (long-term migrants). To be able to estimate such long-term migrants on the basis of the data available, estimation methods have been developed for Germans and foreigners.

7. Accuracy of migration statistics

Since migration statistics are based on a complete count, overall quality is considered as good. Nevertheless, it depends on the accuracy of the data supplied and especially on whether people obliged to register comply with that obligation. On the whole, the coverage of arrivals is more reliable than that of departures because people mostly register when arriving but more frequently fail to deregister when moving abroad. Although part of such missing deregistrations are replaced by administrative deregistrations carried out by the registration offices, it is not possible to determine for a specific period the exact number of missing deregistrations that remained undetected.

Please also note the current notes on the results of migration statistics.

8. Time series – comparability (geographical and over time)

Data processing is based on a uniform methodology and a uniform procedure, so that the geographical comparability is considered as very good.

However, territorial changes may lead to limited comparability over time. This applies in particular to evaluations at municipality level. For instance, the comparability of the results by municipality or administrative district in a Land with previous year’s data is limited if municipalities were incorporated into larger ones or if there was a territorial reform in the reference year. As changes in larger regional units (e.g. Länder) occur less often, the comparability over time is good at this level. It should be noted that results up to reference year 1990 refer to the former territory of the Federal Republic and are therefore not comparable with the data as from 1991.

Limitations of comparability over time may also result from register adjustments performed by registration offices that can lead to a higher number of departures due to more administrative deregistrations. This occurred especially in the years 2008 to 2010, when the tax identification number was introduced and the population registers were reviewed all over Germany.

The results of migration statistics and, consequently, of current development from intercensal population updates are as from reference year 2016 only to a limited extent comparable with previous year’s values. This is due to methodological changes, technical developments regarding data transmission from registration offices to statistical offices, and the changeover to a new statistical processing procedure.

Difficulties regarding the registration of asylum seekers, problems caused by technical changes to the data transmission system and inconsistencies detected in the statistical processing result in a limited accuracy of the results for 2016 and the monthly results for 2017. These problems have largely been eliminated in the final annual results for 2017.

Methodical changes and impact on comparability:

• Up to 2015, the results of migration statistics included the arrivals and departures recorded by the registration offices until the end of the relevant month. As from January 2016, migration statistics changed over to a new data transmission and processing procedure. Because of this, for a transition period, all arrivals and departures with an arrival or departure date in 2015 or 2016 that were reported to the statistical offices between January 2016 and May 2017 were processed for the reference month corresponding to the date of the event (that is, date of arrival, departure or change in housing status). As from June 2017, migration moves have been processed for the reference month in which the registration office reported the event to the statistical office if the event was in the same month – otherwise the migration move has been processed for the month preceding data transmission from the registration office. The modified procedure for 2016 and until May 2017 produced an anticipatory effect, which means that part of the migration moves were included in the statistics earlier than usual. For example, a departure to another country that happened in March 2016 and was reported to the statistical office in February 2017 was included for reference month March 2016 rather than for January 2017, which would be in line with the current principle of processing.
• As from 2016, the results of migration statistics have included only those arrivals and departures whose date (of arrival or departure) was in the reference year or the preceding year. Previously, earlier arrivals and departures were included too, provided that they took place after the 2011 Census reference date. Such earlier arrivals and departures are only relevant for adjustments of population figures through intercensal population updates, not for the migration statistics of the current year. This is why, as from 2016, they have been included only in the intercensal population updates. As a result, the migration figures are slightly lower than in previous years.
• As from 2016, arrivals and departures of Germans “with new/previous residence unknown / no data provided" have includes in the external migration figures, whereas in the past they were not included at all. To determine the population figures, people who had been deregistered “with new residence unknown” and register again are now only processed as arrivals “with previous residence unknown” if the earlier deregistration “with new residence unknown” has been included in the statistics (i.e. if it happened in 2016 or later). As, however, all deregistrations of Germans “with new residence unknown” have been included, the number of registrations “with previous residence unknown” shown is too low when compared with the number of deregistrations “with new residence unknown”, so that the net emigration of Germans shown is too high. This effect is inevitable for methodological reasons and affects especially the results for 2016 and, with a downward trend, the results for subsequent years. The external migration figures of Germans by country of origin/destination are not affected by that methodological change.

Other limitations to the accuracy of the results:

• Inaccuracies have been detected in the registration of asylum seekers. These inaccuracies are mostly attributed to problems in the feedback procedure between registration offices and in the data transmission from the registration offices to the statistical offices. Because of constraints in the legal framework, the statistical offices cannot do much to eliminate these inaccuracies. This means that the accuracy of flow and stock data on asylum seekers is limited for 2016 and 2017.
• The immigration figures for 2016 include delayed registrations of asylum seekers who had entered Germany in 2015 and were registered only in 2016. The number of delayed registrations in Germany is estimated at roughly 90,000 arrivals. The estimate is based on evaluations of citizenships with a high proportion of asylum seekers (Syria, Afghanistan, Iraq, Iran, Pakistan, Eritrea, Somalia, Nigeria, and uncertain citizenship). Adjustments of the population registers regarding asylum seekers whose registered place of residence was an initial reception center and who have moved to another municipality are included in the results for 2016 if the adjustments took place in May 2017 or earlier.
• In the context of the technical changes to the data transmission system and the statistical processing procedure, a number of subsequent problems have been identified. They have led not only to the above methodological effects but also to an overestimation of the number of departures “with new residence unknown” as shown in net external migration and an underestimation of the number of arrivals “with previous residence unknown” as from 2016. This has led to an underestimation of the population of Germany. The quantitative impact on the annual results for 2016 is estimated as follows: underestimation of arrivals “with previous residence unknown” of 9,000 to 10,000 cases, overestimation of departures “with new residence unknown” of 6,000 to 7,000 cases, and underestimation of net migration and of the population of Germany of roughly 16,000 people. Retroactive correction of migration statistics and intercensal population updates released for 2016 is not possible. The detected inaccuracies were largely eliminated from statistics and intercensal population updates until the end of reference year 2017. Corrections of migration moves recorded in the months of 2017 are included in the annual result for 2017 of migration statistics and in the results of intercensal population updates for December 2017. Corrections of migration moves that occurred before 2017 are included only in intercensal population updates.