UNFPA/UNECE/NIDI Training programme on international migration, Geneva, 24-28/01/2005 Analytical Measures and Methods George Groenewold, NiDi 1. 2. 3. Demographic Balance Equation: Method related concepts and definitions Main approaches: A. Migration status is known: direct methods A.1 Cross-tabulation migration status characteristics and an example B. Migration status is unknown: indirect methods B.1 Vital Statistics or Residual Method and an example B.2 Intercensal Cohort Component Method and an example 1. The Demographic Balance Equation P(t+1)= P(t)+Births-Deaths+(Immigrants-Emigrants), or, P(t+1)= P(t)+Natural Increase+Net Migration 2. Method related concepts and definitions Out-migration (emigration) rate: number of persons that moved out of place X divided by the average number of persons that were exposed to migration In-migration (immigration) rate: number of persons that live in place x, but originated from elsewhere, divided by the average number of persons that were exposed to migration Net migration: the difference between the number of immigrants (or inmigrants) and the number of emigrants (or out-migrants) Note: no concensus about which persons should be in the denominator in the above measures (UN, 1970, pp40-42.), depends on research question which one to choose Lifetime migrant: someone who at the time of the census lives away from his/her place of birth Cohort A cohort is a group of individuals experiencing the same demographic (vital) event. Birth cohort=persons born in the same year. Migration cohort=persons who emigrated from country X in the same year. Life table. A life-table summarizes the (age specific) mortality experience in a population in a particular year or particular (intercensal) period. Separate life tables are constructed for men and women. A full life-table can be derived from a set of Age Specific Mortality Rates (ASMR’s). Two important products of the life table are: (1) the life expectancy at birth and (2) age-specific survival ratio’s Survival Ratio. Indicator for the probability of surviving of persons in a particular age-group X to the next higher age-group X+5. Survival ratio’s are used in cohort component projections of the population Cohort Component Projection Method. Estimation method that builds on the principle that the size and age-structure of the current population can be predicted from an age distribution in the past if interperiod births, deaths and net numbers of (international) migrants are known 3. Main approaches: A. Migration status is known: direct method (D) A.1 Cross-tabulation of migration status characteristics • Place of Usual Residence (POR) by Place of Birth -life time migration moves only, not time-specific -severe underestimation migration moves (intermediate destinations not recorded) • POR by POR 1 or 5 years ago Example -focus on recent migration flows -UN recommends 5 years ago -recall problem with fixed reference date • POR by Place of Previous Residence by Duration of Residence -refined migration cohort analysis, and migration and development analysis - recall problem Table 1. Place of (usual) residence at time of census by Place of residence 1 year ago Place of residence one year ago 2001 D.K.B Maekel S.K.B Anseba Gash-Barka Debub Total 2002 pop. MIDPERIOD Population outmigrants outmigration rate (per 1000) inmigrants inmigration rate (per 1000) net number of migrants net migration rate (per 1000) Province of usual residence at census night, 2002 (POR) D.K.B Maekel S.K.B Anseba Gash-Barka 170 9 3 3 9 8 1050 12 8 12 7 8 775 5 13 6 16 5 675 20 9 12 14 9 1080 10 8 8 4 8 210 1103 817 704 1142 Debub 6 22 30 24 15 1580 1677 Total 200 1112 838 746 1139 1618 5653 Table 1. (continued) Place of residence one year ago 2001 D.K.B Maekel S.K.B Anseba Gash-Barka Debub Total 2002 pop. MIDPERIOD Population outmigrants outmigration rate (per 1000) inmigrants inmigration rate (per 1000) net number of migrants net migration rate (per 1000) Province of usual residence at census night, 2002 (POR) D.K.B Maekel S.K.B Anseba Gash-Barka 170 9 3 3 9 8 1050 12 8 12 7 8 775 5 13 6 16 5 675 20 9 12 14 9 1080 10 8 8 4 8 210 1103 817 704 1142 Debub 6 22 30 24 15 1580 1677 Total 200 1112 838 746 1139 1618 5653 205 30 1108 62 828 63 725 71 1141 59 1648 38 5653 323 40 53 42 29 62 97 323 10 -9 -21 -42 3 59 0 Table 1. (continued) Place of residence one year ago 2001 D.K.B Maekel S.K.B Anseba Gash-Barka Debub Total 2002 pop. MIDPERIOD Population outmigrants outmigration rate (per 1000) inmigrants inmigration rate (per 1000) net number of migrants net migration rate (per 1000) Province of usual residence at census night, 2002 (POR) D.K.B Maekel S.K.B Anseba Gash-Barka 170 9 3 3 9 8 1050 12 8 12 7 8 775 5 13 6 16 5 675 20 9 12 14 9 1080 10 8 8 4 8 210 1103 817 704 1142 205 30 146 40 195 10 49 1108 62 56 53 48 -9 -8 828 63 76 42 51 -21 -25 725 71 98 29 40 -42 -58 1141 59 52 62 54 3 3 Debub 6 22 30 24 15 1580 1677 Total 200 1112 838 746 1139 1618 5653 1648 38 23 97 59 59 36 5653 323 57 323 57 0 0 Table 1. (continued) Place of residence one year ago 2001 D.K.B Maekel S.K.B Anseba Gash-Barka Debub Total 2002 pop. MIDPERIOD Population outmigrants outmigration rate (per 1000) inmigrants inmigration rate (per 1000) net number of migrants net migration rate (per 1000) Province of usual residence at census night, 2002 (POR) Anseba Gash-Barka S.K.B Maekel D.K.B 9 3 3 9 170 12 8 12 1050 8 13 5 775 8 7 20 675 5 16 6 1080 9 14 12 9 8 4 8 8 10 1142 704 817 1103 210 Debub 6 22 30 24 15 1580 1677 Total 200 1112 838 746 1139 1618 5653 1141 59 52 62 54 3 3 1648 38 23 97 59 59 36 5653 323 57 323 57 0 0 Debub -4 14 22 20 7 Total -10 9 21 42 -3 -59 0 205 30 146 40 195 10 49 1108 62 56 53 48 -9 -8 828 63 76 42 51 -21 -25 725 71 98 29 40 -42 -58 Province-specific net numbers of migrants Place of residence 1 year ago 2001 D.K.B Maekel S.K.B Anseba Gash-Barka Debub net total migrants 2002 (POR) Province of residence at census night, 2002 (POD) Anseba Gash-Barka S.K.B Maekel D.K.B 0 -3 -4 1 0 -8 4 -1 -1 0 -4 4 11 0 8 3 -11 1 0 0 -7 -20 -22 -14 4 3 -42 -21 -9 10 59 B. Migration status is unknown: indirect methods B.1 Vital Statistics or Residual Method and an example Demographic Balance Equation P(t+1)= P(t)+Births-Deaths+(Immigrants-Emigrants), or, P(t+1)= P(t)+Natural Increase+Net Migration or, Net Migration=P(t+1) - (P(t)+Natural Increase) Indirect estimation: Migration estimate derived as ‘residual’ from two subsequent census populations and intercensal natural increase (=recorded or estimated intercensal births-deaths) Table 2. Derivation of net migration estimates if population figures at two points in time are known and numbers of births and deaths are known between these points in time Net migration to European Union, 2000, (*1000) Population Natural Population 1.1.2000 increase + Natural Increase EU-15 Belgium Denmark Germany Greece Spain France Ireland Italy Luxembourg Netherlands Austria Portugal Finland Sweden UnitedKingdom (1) (2) 376.455,2 10.239,1 5.330,0 82.163,5 10.542,8 39.441,7 59.225,7 3.776,6 57.679,9 435,7 15.864,0 8.102,6 9.997,6 5.171,3 8.861,4 59.623,4 (3) 372,4 10,9 9,0 -76,2 -2,0 27,2 240,6 23,1 -17,2 2,0 66,1 1,5 14,3 7,4 -3,0 68,7 Population Difference 1.1.2001 (5) -(4) Net Migration Estimate (4) (5) 376.827,6 377.507,9 10.250,0 5.339,0 82.087,3 10.540,8 39.468,9 59.466,3 3.799,7 57.662,7 437,7 15.930,1 8.104,1 10.011,9 5.178,7 8.858,4 59.692,1 10.262,2 5.349,2 82.192,6 10.564,7 39.489,6 59.521,3 3.819,7 57.844,0 441,3 15.983,1 8.121,3 10.022,8 5.181,1 8.882,8 59.832,1 680,3 12,2 10,2 105,3 23,9 20,7 55,0 20,0 181,3 3,6 53,0 17,2 10,9 2,4 24,4 140,0 Source: Eurostat Statistics in Focus, Population and social conditions, Theme 3 - 7/2002 Table 2. (continued) Net migration to European Union, 2000, (*1000) Population Natural Population Population Difference 1.1.2000 increase + 1.1.2001 (5) -(4) Natural Increase Net Migration Estimate EU-15 Belgium Denmark Germany Greece Spain France Ireland Italy Luxembourg Netherlands Austria Portugal Finland Sweden UnitedKingdom (1) (2) (3) (4) (5) 376.455,2 372,4 376.827,6 377.507,9 10.239,1 5.330,0 82.163,5 10.542,8 39.441,7 59.225,7 3.776,6 57.679,9 435,7 15.864,0 8.102,6 9.997,6 5.171,3 8.861,4 59.623,4 10,9 9,0 -76,2 -2,0 27,2 240,6 23,1 -17,2 2,0 66,1 1,5 14,3 7,4 -3,0 68,7 10.250,0 5.339,0 82.087,3 10.540,8 39.468,9 59.466,3 3.799,7 57.662,7 437,7 15.930,1 8.104,1 10.011,9 5.178,7 8.858,4 59.692,1 10.262,2 5.349,2 82.192,6 10.564,7 39.489,6 59.521,3 3.819,7 57.844,0 441,3 15.983,1 8.121,3 10.022,8 5.181,1 8.882,8 59.832,1 Total increase (2)+(5) 680,3 (7) 1.052,7 12,2 10,2 105,3 23,9 20,7 55,0 20,0 181,3 3,6 53,0 17,2 10,9 2,4 24,4 140,0 23,1 19,2 29,1 21,9 47,9 295,6 43,1 164,1 5,6 119,1 18,7 25,2 9,8 21,4 208,7 Source: Eurostat Statistics in Focus, Population and social conditions, Theme 3 - 7/2002 Table 2. (continued) Net migration to European Union, 2000, (*1000) Population Natural Population Population Difference Total Rate Net Total 1.1.2000 increase + 1.1.2001 (5) -(4) increase of migration increase Natural Natural Rate % Increase Net (2)+(5) Increase % Annual Migration % Population Estimate Growth Rate (1) (2) (3) (4) (5) (7) (8) (9) (10) EU-15 376.455,2 372,4 376.827,6 377.507,9 680,3 1.052,7 0,10 0,18 0,28 Belgium Denmark Germany Greece Spain France Ireland Italy Luxembourg Netherlands Austria Portugal Finland Sweden UnitedKingdom 10.239,1 5.330,0 82.163,5 10.542,8 39.441,7 59.225,7 3.776,6 57.679,9 435,7 15.864,0 8.102,6 9.997,6 5.171,3 8.861,4 59.623,4 10,9 9,0 -76,2 -2,0 27,2 240,6 23,1 -17,2 2,0 66,1 1,5 14,3 7,4 -3,0 68,7 10.250,0 5.339,0 82.087,3 10.540,8 39.468,9 59.466,3 3.799,7 57.662,7 437,7 15.930,1 8.104,1 10.011,9 5.178,7 8.858,4 59.692,1 10.262,2 5.349,2 82.192,6 10.564,7 39.489,6 59.521,3 3.819,7 57.844,0 441,3 15.983,1 8.121,3 10.022,8 5.181,1 8.882,8 59.832,1 12,2 10,2 105,3 23,9 20,7 55,0 20,0 181,3 3,6 53,0 17,2 10,9 2,4 24,4 140,0 23,1 19,2 29,1 21,9 47,9 295,6 43,1 164,1 5,6 119,1 18,7 25,2 9,8 21,4 208,7 Source: Eurostat Statistics in Focus, Population and social conditions, Theme 3 - 7/2002 0,11 0,17 -0,09 -0,02 0,07 0,41 0,61 -0,03 0,46 0,42 0,02 0,14 0,14 -0,03 0,12 0,12 0,19 0,13 0,23 0,05 0,09 0,52 0,31 0,82 0,33 0,21 0,11 0,05 0,27 0,23 0,23 0,36 0,04 0,21 0,12 0,50 1,14 0,28 1,29 0,75 0,23 0,25 0,19 0,24 0,35 B.2 Intercensal Cohort Component Method and an example • Data needs - Age distributions by sex of two consecutive censuses - intercensal life-tables by sex - Estimate of intercensal fertility (ASFR by sex, or ASFR and sex ratio at birth • The principle 1. Project age groups (0-75 years) in first census, in year t, to the date of the second census using appropriate intercensal life tables for each 5year projection interval: P(t,x) × S(x, x+5)=P(t+5,x+5), where x=age-group 2. Estimate births in 5-year projction interval and project number of surviving births in each 5-year projection interval 3. Repeat (1. ) and (2.) for each five-year projection interval and substract the projected population at the time of the second census from the observed census population to obtain age specific and total net migration estimate (=indirect or residual estimation) Figure 1. Lexis-diagram, illustrating the principle of Cohort Component Projections Step 1: derivation/selection of an appropriate life table Re: model answers, 27 april 2000, GG T a b l e 1 : E x ce rp t f ro m l i fe -t a b le f o r w o m e n i n c o u n t ry X , b as e d o n 1 9 9 1 C en s u s , a s s u m ed to b e re p re s en t at i v e fo r t h e 1 9 9 1 - 1 9 9 6 p e ri o d . AG E 0 1- 4 5- 9 10 -14 15 -19 20 -24 25 -29 30 -34 . . . Et c. . . . . 70 + M(X ,N) .09 649 .01 027 .00 603 .00 340 .00 417 .00 513 .00 581 .00 645 Q(X ,N) .09 056 .04 001 .02 970 .01 687 .02 066 .02 531 .02 866 .03 173 l( X) D(X ,N) L(X ,N) S(X ,N) 10 0000 9 056 9 3857 .8 961 A 9 0944 3 639 35 4231 .9 597 B 8 7305 2 593 43 0044 .9 766 8 4712 1 429 41 9989 .9 815 8 3283 1 721 41 2247 .9 770 8 1563 2 064 40 2773 .9 729 7 9498 2 278 39 1877 .9 698 7 7220 2 450 38 0053 .9 664 To be used in table 3, column 3, rows 4 to 7 .19 611 ... .. 1 7067 17 067 8 7028 T( X) 5 4458 77 5 3520 20 49 9778 9 45 6774 5 41 4775 6 37 3550 9 33 3273 6 29 4086 0 E( X) 54.4 59 58.8 50 5 7.2 45 5 3.9 21 4 9.8 03 4 5.7 99 4 1.9 22 3 8.0 84 To be used in table 2, last row, column last shaded cell .8 580 8 7028 __ ____ ____ ____ ____ ____ ____ ____ A= V A L U E G I V E N I S F O R S U R V IV O R S H I P O F 5 C O H O R T S O F B IR T H T O A G E G R O U P 0 - 4 = L( 0 , 5) / 5 0 00 0 0 B= V A L U E G I V E N I S F O R S ( 0 ,5 ) = L ( 5 ,5 ) /L ( 0 ,5 ) 5 .09 9 Step 2: Estimation of Births and births surviving projection interval Age group Female Female Population Population 1991 1996 (1) (2) Women at Age-Specific risk of child Fertility Estimated bearing Rates Births (1991-1996) (A.S.F.R.) (1991-1996) (3)=((1)+(2)/2) (4) 5 x ((3)x(4)) 15-19 1388 1459 1424 20-24 1269 1327 1298 25-29 1112 1216 1164 30-34 911 1069 990 35-39 716 876 796 40-44 628 690 659 45-49 553 602 578 Total births Proportion of female births (sexratio=1.05) Total female births (1991-1996) Average 5-year survival ratio of newborns (L(0,5)/500,000) Expected deaths among female births (1991-1996) Total surviving female births 0.044 0.172 0.158 0.098 0.045 0.017 0.003 313 1116 920 485 179 56 9 3078 0.4878 1501 0.8961 156 1345 Step 3: Derivation of age-specific net-migration estimates, assuming that second census is five-years later than first census Population Survival Age group Census 1991 Ratio (1) 0-4 5-9 10-14 15-19 20-24 25-29 30-34 35-39 40-44 45-49 50-54 55-59 60-64 65-69 70+ Total 1469 1487 1498 1388 1269 1112 911 716 628 553 470 399 335 268 424 12927 (2) 0.9597 0.9766 0.9815 0.9770 0.9729 0.9698 0.9664 0.9660 0.9609 0.9629 0.9796 0.9373 0.8985 0.8323 0.5880 Projected Population Population Census 1996 1996 (1)*(2) (counted) (3) 1345 1410 1452 1470 1356 1235 1078 880 692 603 532 460 374 301 472 13662 (5) 1297 1412 1453 1459 1327 1216 1069 876 690 602 530 459 373 302 471 13536 Estimated Net Migrants (5)-(4) (6) Surviving intercensus births -48 2 1 -11 -29 -19 -9 -4 -2 -1 -2 -1 -1 1 (268 x 0.8323) + -1 (424 x 0.5880)= 472 -126 • If census is 10 years apart, add another projection interval, I.e. repeat steps 2 and 3 to determine projected population 10 years later. Use different fertility and/or mortality rates if appropriate • This approach may slightly over- or underestimate the above agespecific net migration numbers • Solution: • 1. Reverse survive the survivors observed in the second census to the date of the first census and derive estimate of net number of migrants from that projection. 2. Average the forward and reverse-survived estimate of age-specific net migration For Cohort Component Projections, use software, e.g.: - PEOPLE -FiVFiV - PAS -LIPRO - DemProj - PDPM_PC - MortPak-Lite Suggested literature. - UN , 1970. Manual VI. Methods of Measuring Internal Migration. Population Studies, No. 47. ST/SOA/Series A/47. Department of Economic and Social Affairs New York. - UN, 1992. Preparing Migration Data for Subnational Population Projections. ST/ESA/SER.A/127. Department of International Economic and Social Affairs. New York. - Zaba, B. 1985. Measurement of Emigration using Indirect Techniques. Ordina Editors. Liege - Shryock, H.S. and J.S. Siegel. 1976. The Methods and Materials of Demography. Academic Press, London.