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Analysing Structures of Interregional Migration in England

This session at the ESRC Research Methods Festival delves into the analysis of interregional migration patterns in England using census and registration data. Explore log-linear models, multiplicative components, and observed-to-expected ratios to understand migration behavior shifts over time.

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Analysing Structures of Interregional Migration in England

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  1. Analysing Structures of Interregional Migration in England James Raymer and Corrado Giulietti Southampton Statistical Sciences Research Insitute (S3RI) Session 40: Handling Migration and Commuting Flow Data, ESRC Research Methods Festival, Oxford, 2 July 2008

  2. Context and significance • Context • First part of an ESRC-funded project on combining census and registration migration data in England and Wales • Significance • Helps us to better understand aggregate population change and migration behaviour • Provides a basis for the estimation of migration patterns, including projection

  3. Outline • Introduction • Analysing migration structures • Multiplicative component framework • Log-linear models • Interregional migration in England • Analysis of multiplicative components • Log-linear analyses of migration flow tables • Summary and next steps

  4. Data • 1991 and 2001 censuses • Interregional migration flows in England • Origin (9) by destination (9) by age (16) • Origin (9) by destination (9) by ethnicity (4) • Inconsistencies in measurement over time • Student population • Mixed ethnicity group

  5. Multiplicative component model for a 2-way table: Origin by destination Migration flow table Multiplicative components nij = (T)(Oi)(Dj)(ODij), where T = n++ Oi =ni+ / T Dj = n+j / T ODij = nij / (T)(Oi)(Dj)

  6. Multiplicative Models for Three-Way Tables • Interregional migration by age • Interregional migration by ethnicity Overall Level Main Effects (proportions) Two-way Inteactions (odds) Three-way Interaction (odds ratios)

  7. Log-linear models for analysing structures in three-way migration flow tables • Saturated model: ODE • Unsaturated model (mutual independence): O, D, E • Unsaturated model: OD, E Note, we use the likelihood ratio statistic (G2) and the Akaike Information Criteria (AIC) to compare the overall fits of unsaturated models

  8. Overall levels 1991: 630 thousand 2001: 920 thousand The proportions of all migration from and to each region in England, 1991 and 2001

  9. The observed to expected ratios of interregional migration (ODij) in England, 1991 2.783 = 5,159 / (628,610 * 0.082 * 0.036) = 5,159 / 1,854 0.539 = 6,046 / (628,610 * 0.220 * 0.081) = 6,046 / 11,225

  10. The observed to expected ratios of interregional migration (ODij) from Yorkshire and the Humber and London, 1991 and 2001

  11. Proportions of all interregional migration in England by age, 1991 and 2001

  12. OAix Origin-age and destination-age interaction effects of interregional migration in England, 1991 and 2001: London DAjx

  13. Proportions of all interregional migration in England by ethnicity, 1991 and 2001

  14. OEig DEjg Origin-ethnicity and destination-ethnicity interaction effects of interregional migration in England, 1991 and 2001: White

  15. OEig DEjg Origin-ethnicity and destination-ethnicity interaction effects of interregional migration in England, 1991 and 2001: South Asian

  16. OEig DEjg Origin-ethnicity and destination-ethnicity interaction effects of interregional migration in England, 1991 and 2001: Black

  17. A comparison of unsaturated log-linear model fits: England migration tables cross-classified by origin (O), destination (D), age (A) and time (T) Note, df = residual degrees of freedom

  18. North East to London London to North East Estimated age patterns of migration between North East and London and South West, 2001 A comparison of two unsaturated log-linear models South West to London London to South West

  19. A comparison of unsaturated log-linear model fits: England migration tables cross-classified by origin (O), destination (D), ethnicity (E) and time (T) Note, df = residual degrees of freedom

  20. Estimated South Asian interregional migration from North East and London, 1991 and 2001: A comparison of two unsaturated log-linear models

  21. Main points • Despite a large increase in the level of interregional migration, the underlying structures have remained remarkably stable over time (except with some of the ethnic structures) • Large differences in the patterns occur by age (not much change over time) and ethnicity (lots of change over time) • The three-way interaction terms of the multiplicative model do not contribute much to the overall fit • Future work • Extend analysis to county level and other variables (e.g., education and employment) • Build model for combining census and registration migration data to estimate detailed patterns annually over time

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