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Evaluation of Internal Migration Data Collected from Population Censuses

Evaluation of Internal Migration Data Collected from Population Censuses. United Nations Statistics Division. Outline. Related concepts of internal migration Direct and indirect estimates of internal migration Sample tabulations Discussion on quality issues.

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Evaluation of Internal Migration Data Collected from Population Censuses

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  1. Evaluation of Internal Migration Data Collected from Population Censuses United Nations Statistics Division

  2. Outline • Related concepts of internal migration • Direct and indirect estimates of internal migration • Sample tabulations • Discussion on quality issues

  3. Internal migration – related concepts • Mobility versus migration • Migration refers to “long-distance” move, i.e., moves across states or county lines (usually referring to across administrative unit borders) • Migration  change of place of usual residence • Time element • Geographic moves

  4. Internal migration – related conceptshort and long distance moves Data source: Methods and Materials of Demography, classification based on “1-year” data from the March 2000 Current Population Survey of the US

  5. Internal migration – related concepts (2) • Place of usual residence (UN, 2008) • It is recommended that countries apply a threshold of 12 months when considering place of usual residence according to one of the following two criteria: • The place at which the person has lived continuously for most of the last 12 months (that is, for at least six months and one day), not including temporary absences for holidays or work assignments, or intends to live for at least six months; • (b) The place at which the person has lived continuously for at least the last 12 months, not including temporary absences for holidays or work assignments, or intends to live for at least 12 months. • Difficult to treat groups: • Seasonal residence • work in one place during weekdays and join family member during weekends • College students

  6. Internal migration – related concepts (3) • Lifetime migration: • - Migration occurred between birth and the time of the census • Recent migration: • - Migration occurred in recent period, e.g., 1 year

  7. Internal migration data from censuses • Tabulated from direct questions about mobility or about prior residence • Place of birth • Place of residence at a fixed past date • Duration of residence • Previous place of residence • Estimates of net migration derived from (residual estimates) • Counts of total population or population disaggregated by age and sex, at two censuses • Natural increase or intercensal survival rates, which are derived in turn from (a) life tables or (b) comparison of the age distributions of countries not experiencing immigration or emigration in successive censuses

  8. Internal migration data from censuses – direct method • Place of birth • Civil division of birth for native-borns; usually refers to the geographical unit of the country in which the mother resides at the time of the person’s birth • Country if foreign-born • Place of residence at a specified date in the past • Major or smaller division, or a foreign country • 1 or 5 years, or both • 1 year easier to recall • Different date may be used depends on national circumstances • Duration of residence • Should refer to the length of residence in the major or smaller civil divisions and the locality, but not in the particular housing unit • Place of previous residence • Major or smaller division, or a foreign country

  9. Internal migration data from censuses – direct methodplace of birth (1) Source: The Methods and Materials of Demography, 2nd edition, Siegel and Swanson, 2004

  10. Internal migration data from censuses – direct methodplace of birth (2) Source: The Methods and Materials of Demography, 2nd edition, Siegel and Swanson, 2004

  11. Internal migration data from censuses – direct methodplace of birth (3) • Intercensal migration can be estimated by using data by place of birth from two consecutive censuses • Net migration for an area M = (It+n-Ot+n) – (S1It – S2Ot ) • It: life time in-migrants at time t • It+n: life time in-migrants at time t+n • Ot: life time out-migrants at time t • Ot+n: life time out-migrants at time t+n • S1: proportion of life time in-migrants It that will survive to time t+n • S2: proportion of life time out-migrants t that will survive to time t+n

  12. Internal migration data from censuses – direct methodplace of birth (4) Source: Manual VI: Methods of Measuring Internal Migration, United Nations, 1970

  13. Internal migration data from censuses – direct methodplace of birth (5) • Quality issues: • Memory problem • Uncertainties about area boundaries at the time of birth • Errors in reporting of birthplaces for babies who were not born at the usual residence of their parents • Reporting birthplace according to the old administrative boundaries • Reporting place of births like hospitals rather than place of usual residence of the mother

  14. Internal migration data from censuses – direct method place of birth (6) • Ways to assess data quality: • re-interviews or matching studies of a sample of the original records (US census Bureau, 1995, p.19) • Study the impact of boundary changes: • Lee et al. 1957 • Compare between censuses or with household surveys

  15. Internal migration data from censuses – direct methodresidence at a fixed past date (1) Source: Statistics Bureau of Japan

  16. Internal migration data from censuses – direct methodresidence at a fixed past date (3) • Information may be used to get a sense of “flow”: annual in-migrants and out-migrants for different areas.

  17. Internal migration data from censuses – direct methodresidence at a fixed past date (4) • Quality issues: • Memory problem, the longer the period used, the less accurate the information is • Mis-reporting of previous residence • Change of boundaries

  18. Internal migration data from censuses – direct methodduration of residence + previous residence (1) Distribution of lifetime migrants by duration of stay in each State Source: Manual VI: Methods of Measuring Internal Migration, United Nations, 1970

  19. Internal migration data from censuses – direct method duration of residence + previous residence (2) For recent migrants: longer distance  more migrants Source: Manual VI: Methods of Measuring Internal Migration, United Nations, 1970

  20. Internal migration data from censuses – direct methodduration of residence + previous residence (3) Origin, destination and time of migration (duration): Source: Manual VI: Methods of Measuring Internal Migration, United Nations, 1970

  21. Internal migration data from censuses – direct methodduration of residence + previous residence (4) • Quality issues: • Memory problem, might not remember when moved • Digit preference (similar to those reflected in age-reporting)

  22. Internal migration data from censuses – indirect method National growth rate method (1) • National growth rate method – for net internal migration Population of area i in the first census Population of area i in the second census Total population of a country in the first census Total population of a country in the first census Positive rate: with net inmigration; negative rate: net outmigration Assumes same natural increase rate and net immigration from abroad for all parts of the country

  23. Internal migration data from censuses – indirect method National growth rate method (2) • National growth rate method – example Data source: graph produced based on data from United Nations Demographic Yearbook

  24. Internal migration data from censuses – indirect method Vital statistics method (1) • Vital statistics method for net migration rate Births nationally during the intercensal period Deaths nationally during the intercensal period Calculate net migration rate (incl. both internal and international migration) Assumes same natural increase rate across all areas

  25. Internal migration data from censuses – indirect method Vital statistics method (2) Vital statistics method – example Data source: graph produced based on data from United Nations Demographic Yearbook

  26. Internal migration data from censuses – indirect method Survival rate method (1) • Survival-rate method Net migration for the cohort aged x at year 0 to year t Population size for cohort x (at year 0) at year t Survival rate of the cohort from year 0 to year t Population size for cohort x at year 0 Adjustment for deaths of migrants during the period s can be calculated by

  27. Internal migration data from censuses – indirect methodSurvival rate method (2): Vienna, Austria Tabulated based on data obtained from Austria Statistics Office online database

  28. Possible concerns/errors to use indirect method • Change of area boundaries • Mixture with international migration • Depends on errors in all components: • Population by age and sex • Births • Deaths

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