832. The United Nations Recommendations on Statistics of International Migration and Temporary Mobility⁸² refer to the concept of international mobility that includes all movements that cross international borders within a given year. Within this broad concept, international migration is defined as a change in the country of residence whereas international temporary mobility includes all other international border crossings (events).

833. In previous rounds of population censuses, the focus of the recommendations was on international migration without reference to temporary migration. However, temporary migration can have significant societal and economic consequences, similar to those of international migration. Due to the potential impact on the society and the economy and the increasing need to collect information on temporary populations, the United Nations Recommendations on Statistics of International Migration and Temporary Mobility recognize the importance to collect information on international temporary mobility, in addition to international migration. Collecting information on temporary populations is recommended for the censuses of the 2030 round. All information regarding temporary populations is considered as non-core, given the difficulties of collecting information on this topic and the specificities of groups of interest depending on the country.

834. National legal frameworks and country-specific contexts need to be considered when planning and conducting the enumeration of all mobility (including temporary mobility) populations, and when developing concepts to capture their characteristics and attributes. The present recommendations apply regardless of whether countries are collecting census data through direct enumeration, or using administrative registers or other sources.

835. There are three different aspects relevant to migration and mobility that can be identified through the census:

(a) Measurement of stocks and in-flows of international migrants and of other groups relevant to international migration, with information on timing and geographical patterns of their international migration;

(b) Measurement of stocks and in-flows of temporary populations (if possible), with information on the timing and geographical patterns of their mobility (this may not be possible in some countries, namely those using data from registers); and

(c) Measurement of stocks and flows of internal migrants, with information on the timing and geographical patterns of their internal migration.

836. Two population groups relevant to international migration are usually identified in population censuses among those with usual residence in the country: the foreign-born population and the population with foreign citizenship (incl. stateless population):

(a) Foreign-born population consists of persons whose place of birth is in another county. This group corresponds to the stock of international migrants that migrated at least once in their lives and reside outside their country of birth at the census reference time. Persons born in the country are defined as “native born”;

(b) Foreign citizens do not have the citizenship of the country and are citizens of another country, or are stateless. Foreign citizens are predominantly foreign born. However, depending on the citizenship laws of certain countries, some children born in the country to foreign-citizen parents may be legally classified as part of the foreign citizen population. Alternatively they may automatically be granted the right of citizenship of the country and considered to be “native born” and therefore not part of the foreign citizen population. Persons having the citizenship of the country are defined as “citizens” or “nationals”.

837. Information may be collected in the census that can provide a classification of the population based on the following topics:

(a) Joint use of “country of birth” and “country of citizenship”; or

(b) Joint use of “country of birth”, “country of citizenship” and the country of birth of parents.

838. These topics are discussed below. Based on the two core topics - “country of birth” and “country of citizenship” - the following population groups, identified in Table 4, can be classified:

(a) Native-born:

i. Citizens or nationals: persons born in the country with the citizenship of the country. This group largely comprises native-born persons with national background. This group comprises the population groups (1), (5) and (9) as classified in Table 4. It also includes descendants of foreign-born persons who acquired citizenship of the country after birth;

ii. Foreign citizens: persons born in the country without citizenship of the country (population groups (2), (6) and (10) in Table 4). This group mostly consists of descendants of the foreign born who have not acquired the citizenship of the host country. In most countries this population group will represent only a small proportion of the overall population;

(b) Foreign-born:

iii. Citizens or nationals: persons born abroad with the citizenship of the host country (population groups (3), (7) and (11) in Table 4. This group largely consists of persons with parents of national background who were born abroad, or of persons with foreign background who have acquired host country citizenship;

iv. Foreign citizens: persons born abroad without the citizenship of the country (population groups (4), (8) and (12) in Table 4). This group includes foreign-born immigrants who have not acquired the citizenship of the host country.

839. Based on the same two core topics together with the non-core topic “country of birth of parents”, the following alternative classification of population groups is identified in Table 4:

(a) Descendants of foreign born: This group consists of persons born in the country with at least one parent born abroad (population groups (5), (6), (9) and (10) in Table 4. In population censuses, the focus is generally restricted to those persons whose parents were born abroad (often referred to as “second generation immigrants”). Third generations descendants of foreign-born parents can only be distinguished if the country of birth of grandparents is also collected in addition to that of the parents;

(b) Persons whose parents are of mixed country of birth background: These are defined as persons with one parent born in the country and the other parent born abroad (population groups (9)–(12) in Table 4). This group can represent a significant and growing share of the population in some countries. It is recommended that, if possible, this group should be shown separately in census outputs;

(c) International migrants: The Recommendations on Statistics of International Migration and Temporary Mobility⁸³ define an international migrant as “a person who has changed his or her country of usual residence and established a new residence in the country within a given year”. According to this definition, the stock of international migrants present in a country is defined based on duration-of-stay criteria in accordance with the usual residence concept specified in Chapter 12 (paragraph ‎764), using one of the following criteria: a) the place where the person has lived continuously for most of the preceding 12 months (that is, for at least 6 months and one day), not including temporary absences for holiday or work assignment, or intends to live for at least 6 months and one day; b) the place where the person has lived continuously for at least the preceding 12 months, not including temporary absences for holiday or work assignment, or intend to live for at least 12 months. This group includes all foreign born (population groups (3), (4), (7), (8), (11) and (12) in Table 4) plus those native born who have ever resided abroad.⁸⁴ This group encompasses recent arrivals (provided they meet the criteria of actual or intended duration of stay to be considered residents) as well as persons who may have migrated to a country (called the host country) and have resided in this country for many years. Some may have obtained the citizenship of the host country, while others may still be considered foreign citizens.

Country of birth of parents	Country of birth	Citizenship	Description of the population group
Both parents born in country of census	Born in country of census	Citizen or national	1. Native-born nationals with national background: persons with the country’s citizenship and whose parents were born in the country. This group usually includes the large majority of the population.
		Foreign citizen	2. Native-born foreign population with national background: foreign citizens who were born in the country and whose parents were also born in the country. In practice this usually constitutes only a small population group. It may include members of the so-called “third generation”, persons with double citizenship who report only the foreign one or other persons with special cases.
	Born abroad	Citizen or national	3. Foreign-born nationals with national background: nationals who were born abroad but whose parents were born in the country. This group usually includes children of emigrants returned to the country of origin of their parents. This group can be sizeable, especially in countries that have experienced large emigration flows in the past. Foreign-born adopted children will also be part of this group.
		Foreign citizen	4. Foreign-born foreign population with national background: foreign citizens who were born abroad but whose parents were born in the country. Children of former emigrants can also be included in this group, if not entitled to national citizenship. This group is usually small.
Both parents born abroad	Born in country of census	Citizen or national	5. Native-born nationals with foreign background: persons born in the country whose parents were born abroad. This group includes children of international immigrants who have got the citizenship of the host country, either at birth or by naturalization.	These two groups jointly form the group of descendants of foreign born. This group is also defined as native born with foreign background	Persons with foreign background	Part of 'second generation’
		Foreign citizen	6. Native-born foreign population with foreign background: foreign citizens born in the country but whose parents were born abroad. In this group there are children of immigrants who did not get the citizenship of the host country.
	Born abroad	Citizen or national	7. Foreign-born nationals with foreign background: nationals born abroad whose parents were also born abroad. This group includes the foreign-born immigrants who got naturalized.	These two groups jointly form the foreign born with foreign background. This group is often referred to as the “first generation”.
		Foreign citizen	8. Foreign-born foreign population with foreign background: This group includes the foreign-born immigrants living in the host countries and keeping their original citizenship. In many countries this is the largest group among all those with foreign background.
Mixed (one parent born in the county and one born abroad)	Born in country of census	Citizen or national	9. Native-born nationals with mixed background: persons with the country’s citizenship born in the country with one parent born in the country and another born abroad. This is usually a small population group, but it can be sizeable in countries with high immigration.		Persons whose parents are of a mixed country of birth background	Part of 'second generation’
		Foreign citizen	10. Native-born foreign population with mixed background: foreign citizens who were born in the country with one parent born in the country and another born abroad. In practice this is a small population group in most countries, since citizenship would be acquired either through ius soli or through ius sanguinis.
	Born abroad	Citizen or national	11. Foreign-born nationals with mixed background: nationals who were born abroad with one parent born in the country and another born abroad. This group usually includes children of emigrants returned to the country of origin. This group can be sizeable, especially in countries that in the past experienced large emigration flows.
		Foreign citizen	12. Foreign-born foreign population with mixed background: foreign citizens who were born abroad with one parent born in the country and another born abroad. Children of former emigrants can also be included in this group, if not entitled to national citizenship. This group is usually small.

840. The groups defined above are not mutually exclusive and they can overlap to a great extent (Figure 3). However, each group is relevant to different aspects of the migration and integration process and represents a potential target for different programs and policies. The size of each group clearly depends on the country, its legislation and its migration history.

841. The group of persons with a foreign background is composed of those persons whose parents were both born outside the country (population groups (5)–(8) in Table 4). Members of this group may or may not have directly experienced an international migration.

842. Persons whose parents were born in the country form the group with a national background (population groups (1)–(4) in Table 4). As noted in paragraph ‎iv ‎(b), those persons who have one parent born in the country and the other born abroad form the group with mixed country of birth background (population groups (9)–(12) in Table 4).

843. Countries that do not ask for country of birth of parents but do ask about acquisition of citizenship can approximate information on foreign/national background by using the following rules:

(a) Persons having national citizenship since birth will be considered as having national background;

(b) Persons who have received national citizenship by naturalization or other means will be considered as having foreign background; and

(c) Persons without national citizenship (that is all foreign citizens) will be considered as having foreign background.

844. When using the topic on citizenship acquisition (see para. ‎861) to identify national/foreign background, the following issues should be considered:

(a) Persons with foreign background cannot be identified if, by the time of their birth, their foreign-born parents had already acquired the citizenship of the country; and

(b) Persons whose parents are of mixed country of birth background cannot be identified using the topic of citizenship acquisition.

845. Persons with national/foreign background cannot be identified through information on citizenship acquisition in countries where granting of citizenship is based on the country of birth (the jus soli principle).

846. Analytical classifications can be built by using jointly “country of birth”, “country citizenship” and “country of birth of parents”. The classifications built using respectively place of birth/citizenship and place of birth/place of birth of parents/citizenship are particularly important since they allow the identification of various population groups relevant to international migration. A full description of these classifications is given in Table 4.

847. In all topics related to international borders (country of birth, country of birth of parents, country of citizenship, country of previous or current residence), reference should be made to the boundaries existing at the census reference time. If there have been boundary changes that have affected the designation of a person’s country of birth since the birth, it may be necessary to make an allowance for them in order to record the person’s current country of birth. This can have important implications in countries that originated from the splitting of a former country, since many persons that moved within the borders of the former country may now be counted as international migrants, if reference is made to their country of birth or their country of previous residence. It is therefore important to pay attention to the interpretation of data from these countries, particularly in relation to these two topics.

848. Wherever possible, complementary tabulations on population stocks relevant to international migration should be provided, distinguishing persons who migrated before the break-up of the former country from those who did so after the break-up. Persons who were born in a particular territory but whose country of birth has changed due to boundary changes should not be counted as foreign born.

849. Information on country of birth is essential for the analysis of international migration. As a measure of internal migration countries may need to collect information on place of birth within the country – see paragraph ‎880)

850. The country of birth is the country in which the place of birth of a person (see paragraph ‎880) is located. Country of birth is used to distinguish between native-born and foreign-born residents. It should be noted that the country of birth of a person is not necessarily the same as his or her country of citizenship, which is a separate census topic (see paragraphs ‎856-‎860). The country of birth may refer either to the country where the physical birth occurred or to the country in which the mother was usually resident at the time of the birth if this is different. Countries should explain the concept adopted in the census report(s) and any accompanying metadata.

851. For purposes of international comparability, as well as for internal use, information on country of birth should be collected based on international boundaries existing at the census reference time. It is recommended that the information on this topic be collected and coded in the most feasible detailed manner. For the foreign-born population, the collection of information on the specific country of birth is recommended so as to permit the classification by country based on the three-digit alphabetical codes presented in the classification issued by the United Nations Statistics Division.⁸⁵ For respondents who were born outside of the country of enumeration but cannot identify their country of birth, at least the continent or region where that country is located should be collected.

852. Countries may consider including a category “born in the country”, in their outputs, based on the boundaries at the time of the event for those countries where it may be sensitive to describe some respondents as “foreign born” if they had had to leave their place of residence because of war or political disruption. In general, the “foreign-born” category should refer to where there has been an act of physically crossing a national border.

853. Countries with a significant number of immigrants may want to collect information on the country of birth of both parents. This information on the country of birth of parents (father and mother) should be collected of all resident persons adopting the same criteria as for country of birth. This topic permits the identification of the group of descendants of foreign born. Special attention should be paid in collecting this topic in countries where boundaries have undergone major changes (see paragraph ‎847).

854. Information on country of birth of parents can be used, in combination with information on country of birth of the enumerated person, to identify native-born children of the foreign-born population (the so-called “second generation”), as well as to study the integration processes and outcomes of migrants and their descendants. Moreover, in countries that have experienced return migration, information on this topic allows the identification of foreign-born children of native-born parents.

855. In case of adopted children, reference should always be made to the legal parents rather than to the natural parents.

856. Citizenship is defined as the particular legal bond between individuals and their countries, acquired by birth or naturalization according to national legislation. Citizenship is used to identify the population of foreign citizens, that is, those persons resident in the country but who do not hold the citizenship of that country of enumeration.

857. Country of citizenship should be collected separately from information on country of birth as the two are not necessarily the same.

858. Information on country of citizenship should be collected for all persons and coded in the most feasible detailed manner, based on the three-digit alphabetical codes presented in the classification issued by the United Nations Statistics Division.⁸⁶ This classification of countries and areas serves as a useful tool for developing a classification of citizenships. Attention should be paid in considering those dependent territories included in the classification above but that may not have their own citizenship. For reasons of international comparability, each country should collect information on country of citizenship according to the list of countries recognized by the United Nations, rather than whether it recognizes a particular country.

859. Provisions should be made to identify stateless persons, that is, persons who are not considered as citizens or not considered as nationals by any state under the operation of its law.⁸⁷ The category “stateless persons and those without a recognised nationality status” is considered suitable for the census. It is not likely in censuses to be able to fully distinguish those who are stateless (without a recognised statelessness status) from those whose nationality is unclear.⁸⁸

860. Information on all citizenships held by respondents should be collected, to identify the population with dual or multiple citizenships. It is recommended that when collecting information on dual citizens consideration be given to which is the first and the second country of citizenship with the first being the reporting country, which is the country of citizenship where the respondent lives.⁸⁹

861. Countries with a significant number of naturalized persons may want to collect information on the year of acquisition of national citizenship and the way it was acquired, either at birth, by marriage or naturalization, or by some other means according to the national legislation.

862. In countries that have emerged from the break-up of former states, an additional typology of citizenship acquisition may be added which should refer to those who received national citizenship when the new state was created. This typology should include those who were recognized as national citizens when the regulation on citizenship of the newly created state came into force.

863. This topic focuses on all persons who have ever resided outside the current country of usual residence, regardless of country of birth or citizenship, and regardless of other changes of usual residence that may have occurred inside the country. In order to collect information on this topic, individuals should be classified depending on whether or not they have ever had a usual residence abroad. Information on this topic allows the identification of all international migrants (see paragraph ‎iv‎(c)). For those who have ever resided abroad, the year of arrival in the current country of residence should also be collected.

864. The purpose of this topic is to measure duration of residence of international migrants in the host country. It is preferable to measure duration using the year of arrival, rather than the number of years elapsed since arrival in the country, because time of arrival is likely to yield more accurate information.⁹⁰ In order to have more detailed information on the time of arrival, information may also be collected on the month of arrival.

865. The year of arrival should be the calendar year when the person most recently established usual residence in the country. Accordingly, guidance to enumerators and respondents should emphasize that this topic relates only to the most recent immigration to the country since difficulties of understanding may occur where a person has undertaken multiple migrations and established residence in the country on more than one occasion. Recording the year of arrival provides an alternative to pre-coded answers in terms of time intervals for most recent arrival.

866. Some countries may, for national policy needs, also wish to collect information on the year that permanent residency was granted for international migrants. This may be different from the year of arrival, and provides a measure of the duration of the time permanent residency (that is, the legal right to live in a country as a permanent resident) was granted. Likewise, some countries may also choose to collect the year of first arrival to derive the entire period of duration in the country, which may be useful in conducting studies on immigrant integration (see also paragraph ‎870 below).

867. For persons that have ever resided abroad, the country of previous residence may also be recorded. This should be the country in which the person last established a usual residence prior to the move to the country of enumeration. This may not necessarily be the country from which the person travelled to the country of enumeration.

868. For purposes of international comparability, as well as for internal use, information on country of previous residence should be collected on the basis of international boundaries existing at the census reference time. It is recommended that the information on this topic be collected and coded in the most feasible detailed manner, based on the three- digit alphabetical codes presented in the classification issued by the UN Statistics Division.⁹¹

869. Place of previous usual residence within the country should be collected as a separate topic for all persons (see paragraph ‎884). It is an important topic for analysis of internal migration as well as to capture information on returning nationals to the home country.

870. This topic focuses on the total duration of residence in the country of international migrants. Total duration is defined as the total number of years that the international migrant has resided in the country, taking into account all periods of residence including the current one. This topic provides additional information with respect to the year of most recent arrival (see paragraph ‎863 above) for those persons who have established residence in the country on more than one occasion.

871. Some countries may wish to collect information on reasons for international and/or internal migration and/or temporary mobility. This topic should refer to the main reason that drove the respondent to undertake the most recent mobility move. It is recommended that only one main reason for migration be recorded. It may be most appropriate to include this topic as a sub-topic of the item on residence abroad (see paragraph ‎867) or as a sub-topic of the item on the previous place of usual residence (see paragraph ‎884).

872. Examples of some of more common reasons for migration and temporary mobility are:

(a) Work (including to invest or start a business) or employment (including military service);

(b) Education and training;

(c) Marriage, family reunification or family formation;

(d) Forced displacement (e.g. refugees, asylum seekers, people with temporary protection status);

(e) Deportation or involuntary return;

(f) Housing;

(g) Health;

(h) Retirement;

(i) Environment and climate;

(j) Social and political factors.

873. The International Recommendations on Refugee Statistics (IRRS) adopted by the United Nations Statistical Commission in March 2018 (Decision 49/115),⁹² provide a set of specific recommendations to improve the collection, collation, disaggregation, reporting and overall quality of statistics on populations forcibly displaced across borders. The recommendations are intended to help those countries that wish to collect information on this topic to improve national statistics on the stocks and flows and characteristics of refugee and refugee related populations, and to help make such statistics comparable internationally.

874. In this chapter, it is recommended to adopt the 2018 Statistical Framework of the Recommendations, in particular referring to the different groups belonging to refugee and refugee-related populations with reference to collecting data on stock and flows.

875. The population in scope of these recommendations includes refugees, asylum seekers, those admitted for subsidiary, complementary and temporary forms of protection, and others admitted for other international protection reasons. It also includes people who have returned home after seeking international protection. Additionally, it includes those who are not refugees themselves, but have a refugee background, such as naturalized former refugees, children born to refugee parents who are not refugees themselves, and reunified family members from abroad. It is important to note that the recommendations only include persons entering the country to flee from persecution, disturbed public order, war or violence in the country of origin, or those with a similar background. Persons migrating to a country due to economic deprivation, or due to climate change and other human-made disasters in their home country are excluded from the scope of these recommendations, unless they also are in need of international protection to the extent that they cannot return home. In the data collection process of those countries that wish to collect such data, it's recommended to distinguish between the three main groups in the scope:

(a) Persons in need of international protection, including prospective asylum seekers, asylum seekers, persons with determined protection status (refugees, those admitted for complementary and subsidiary forms of protection, and those admitted for temporary protection), and others in refugee-like situations;

(b) Persons with a refugee background, comprising naturalized former refugees, children born to refugee parents, reunified refugee family members from abroad and others with a refugee background;

(c) Persons returned from abroad after seeking international protection. This category includes repatriating refugees, repatriating asylum seekers, persons returning from international protection abroad and others who are returning from seeking international protection abroad.

876. Temporary mobility refers to all persons who were present in the country of enumeration at the reference time but were not residents. Including, for example, those associated with daily commuting, tourism, pilgrimage, business, health care, visits to family or friends, employment (seasonal labour) and education. Temporary populations include forcibly displaced persons who stay in the country of enumeration for less than the minimum duration required in order to be considered part of the resident population, such as asylum seekers in transit, refugees who move to another country or return, and environment or climate related mobility.

877. Some countries may be interested in meeting their own needs, collecting information about the size and characteristics of the temporary population and its characteristics, as well as information about flows of this type of mobility. For these countries, it is recommended to collect data on temporary populations in the 2030 round of censuses. Some countries may be interested in collecting data only on some types of temporary populations. In any case, countries that decide to collect data on temporary populations are encouraged to collect data on the reason for their presence in the country of enumeration and collect social and economic characteristics similar to those collected for international immigrants, in particular characteristics such as country of birth, country of citizenship, and date of arrival to the country. Emphasis is recommended on movements associated with: (a) the labour market (cross-border workers, engaged in seasonal work, other types of employment); (b) utilization of education or training services; (c) utilisation of health care or medical care services; and (d) asylum seekers and those with protection as refugees.

878. Internal migrants are broadly defined as persons who are usually resident in a particular geographical area and who have previously been resident in another geographical area in the country of enumeration. Internal migrants, as identified in the census, are, therefore, specifically defined as those who are usually resident in a civil division at the census reference time and who have previously been resident in another civil division within the country. In order to provide relevant information on internal migrants, a detailed classification should distinguish local, intra-regional or inter-regional moves (as well as any international moves). Geographic areas and civil divisions are defined by each country, but movements within the smallest civil divisions should be considered as “residential mobility” rather than internal migrations.

879. Persons who are international migrants – who, regardless of country of birth or citizenship, have at some point in their lives been usually resident in another country – may also be counted as internal migrants if, after their international move, they have also moved internally and they were resident elsewhere in the country prior to the census.

880. Place of birth is relevant for the analysis of internal migrants. Place of birth can be collected according to either the geographical unit in which the birth took place or to the place of usual residence of the mother at the time of the birth. Countries should collect information according to the criterion that best suits their information needs. Some countries may collect information according to both criteria. As with the topic “country of birth” (paragraph ‎849), countries should explain the concept adopted in the census report(s) and any accompanying metadata. For persons born in the country, information on the smallest civil division should be collected. For persons born outside the country, it is sufficient to collect information on the country of birth.

881. Information on place of birth of the native-born population is primarily used to investigate internal migration. However, for countries that have been recently formed from parts of previously separate entities, such information may be of use in assessing the relative size of population segments from each of those entities and their distribution throughout the country.

882. For the latter purpose, it is usually sufficient to collect information only on the major civil division (state, province or department, for example) where the place of birth is located. If desired, more detailed information on smaller civil divisions can be collected and used for accurate coding of the major division or for presenting data for smaller areas. However, to assist in such coding, a detailed and accurate index of place names, linking the smaller civil divisions to its higher geography is required.

883. For studies of internal migration, data on place of birth in terms of major civil divisions alone are inadequate. For an understanding of movements of people since birth, it is necessary to collect information as required according to the information needs of a country, bearing in mind that (a) the boundaries of administrative units such as cities and other civil divisions may change over time, which will give rise to ambiguity in data reported; and (b) the costs of coding reported data to these smaller units may be prohibitive especially where there are many units and the population is highly mobile. To overcome the first problem, to the extent possible both national and sub-national boundaries should refer to the boundaries applying at the census reference time. Countries should address the second problem in the light of their own circumstances.

884. This topic provides information on geographic and time patterns of migration moves to the current place of residence. It is recommended that the place of previous residence should be identified in terms of the smallest civil division.

885. In operational terms this topic can be implemented in two modes:

(a) Extensive mode: by enquiring into “year and month of arrival in the current place of usual residence” plus “previous place of usual residence”; or

(b) Reduced mode: by enquiring into “place of usual residence one year prior to the census”.

886. In the extensive mode, year and month of arrival should be the calendar year and month when the person most recently established residence in the current place of usual residence. The information is important for measuring both long- and short-term internal migration. In order to reduce the burden on respondents’ (when information is collected in the field), month of arrival could be asked only of those who arrived in the calendar year before the census.⁹³ The previous place of usual residence should be defined in terms of the smallest civil division. From the joint use of the two topics it is possible to analyse patterns and timing of internal migration. If previous place of usual residence was outside the country, the country of residence should be collected (see paragraph ‎867).

887. The reduced mode is primarily intended to allow patterns of recent migration to be studied. If the place of usual residence one year prior to the census was within the country, the smallest civil division should be identified. If the place of usual residence one year prior to the census was outside the country, only the country of residence need be collected (see paragraph ‎867 above).

888. The information on persons that arrived in the current place of residence during the last year collected through the reduced mode can be compared to the corresponding information provided by the extended mode. However, the extensive mode also provides important information on migrations events that took place in previous years. Countries should select either one or the other of the two modes based on their information needs.

889. However, both the extensive and reduced mode provide only partial information on international migration, and it is therefore recommended that countries include the topic “ever resided abroad and year of arrival in the country” (see paragraph ‎863 above) to collect more precise information on the timing of international migration.

890. If information on the place of usual residence one year prior to the census is collected (in the reduced mode of the topic “place of usual residence and date of arrival in the current place”), the place of usual residence five years prior to the census could also be collected. This extension of the time interval allows the capture of a larger number of moves but at the cost of an increased uncertainty about the exact timing of the migration. As with the one-year enquiry, if the place of usual residence five years prior to the census was within the country, the smallest civil division should be identified, but if the place of usual residence was outside the country, only the country of residence need be collected.

891. Some countries may wish to collect information on reasons for internal migration, especially when the country intends to collect data on internally displaced persons. This topic should refer to the main reason that drove the person to undertake the most recent migratory move. It is recommended that only one main reason for migration be recorded. Examples of more common reasons are listed in paragraph ‎872.

892. The 2020 International Recommendations on Internally Displaced Persons defines IDP as the situation of persons who have been forced or obliged to leave or abandon their homes and who have not crossed an internationally recognized border.

893. In countries where massive flows of internal migration have occurred because of dramatic events like wars, social or political unrest, natural or environmental disasters, it is important to measure the magnitude of such movements. However, the count of the stock of IPDs is often difficult to enumerate because of multiple occurrences of movements and diversity of causes of mobility, as well as because of protection concerns or risks attached to such movements. Nevertheless, countries may have specific legal and administrative responsibilities for administering the needs of IPDs, for which information collected in the census would be required. At the international level, it is recommended that countries that wish to collect data on this topic adopt the statistical framework that distinguishes between four main categories on official statistics:

(a) IDPs (or persons who have displacement-related protection needs and vulnerabilities). This group is considered the main group and it is proposed to divide it into three subcategories according to the location of the persons who still need protection and to vulnerabilities at the measurement time: 1. Persons who are located in the displacement location (IDPs in locations of displacement); and, 2. Persons who returned to their place of habitual residence (IDPs in locations of return); and 3. IDPs who have settled elsewhere in the country (IDPs in other settlement locations);

(b) Children of at least one IDP parent: Should be counted as a separate but related statistical category;

(c) Other non-displaced family members of IDPs: Should not be included as a statistical category in official IDP statistics;

(d) Those who have overcome key displacement-related vulnerabilities: No longer within the stock of IDPs but recommended to be reported on as a separate statistical category. It is proposed to divide this group into three subcategories according to the location of the persons who are no longer within the stock on IDPs: 1. persons who integrated in the displacement location (Locally integrated); 2. persons who returned and reintegrated in their place of habitual residence (Returned and reintegrated); and 3. persons who have settled and integrated elsewhere (Settled elsewhere and integrated).

894. It is recommended to refer to the stock and flows statistics of the IDPs. New cases in the stock (inflows) include individuals defined as IDPs (according to the three categories defined above – category a) and include births of women who are IDP or whose father is IDP (category b). Outflows include persons who are No longer within the stock of IDPs (category d), emigration of IDPs and deaths of IDPs.

895. It is recommended to derive data on IDPs using the cause of internal migration topic. It should be noted that for some groups, the question about the reason for internal migration may not be sufficient to derive the required information. Especially "persons who returned to their place of habitual residence" and "persons who are no longer within the stock of IDPs.". Therefore, it may be necessary to add additional questions to collect all the required information.

896. Further relevant details, such as date of arrival and main reason of displacement, the place of previous residence and the place of current residence are important characteristics of IDPs and may be obtained by cross-tabulation with other topics.