HUMAN FERTILITY DATABASE DOCUMENTATION: BULGARIA

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1 HUMAN FERTILITY DATABASE DOCUMENTATION: BULGARIA Authors: Yordan Kalchev Head of Dvson, Populaton Statstcs, Natonal Statstcal Insttute, Sofa, Bulgara Е-mal: Nadezhda Karlzhova Chef Expert, Populaton Statstcs, NSI Е-mal: Kryštof Zeman Venna Insttute of Demography Е-mal: Last revson: 26 October 2011 WARNING: Due to the low qualty of data pror to 1960, very detaled data are not relable for ths perod. Cohort fertlty ndcators, ncludng data on chldlessness and party dstrbuton, should be used wth the greatest cauton (see secton 5). 1 General nformaton Ths report descrbes statstcal data provded by the Natonal Statstcal Insttute, Bulgara, to the Human Fertlty Database (HFD). The data nclude the number of lve brths by age of the mother, mother s year of brth, and brth order; the number of lve brths by month; and the female populaton by age and party (number of lve-born chldren) from the populaton census carred out on 1 March Data on brth counts provded for the HFD and descrbed n ths report orgnate from offcal vtal statstcs publcatons as well as from ndvdual brth records. 1.1 Bref hstory Bulgara s located n South-Eastern Europe and occupes the eastern part of the Balkan Pennsula. The borders of the present Republc of Bulgara have not changed snce Snce 1991, Bulgara has been a republc wth a parlamentary form of government. Bulgara joned the European Unon n Accordng to the 2001 census, Bulgara had 7,928,901 nhabtants, of whom 83.9% were of Bulgaran ethncty, 9.4% were Turksh, and 4.7% were Gypses (Roma). The remanng 2% of the populaton consst of around 40 ethnc mnortes, and those who dd not respond to questons about ethncty. The populaton of Bulgara has declned rapdly over the last two decades. The populaton was near to nne mllon n 1989, but ths fgure had dropped to 7.6 mllon at the end of 2008, especally due to emgraton, but n part also because of very low fertlty. As a result of ongong soco-economc and poltcal changes, as well as deteroratng lvng condtons snce 1990, there have been sgnfcant shfts n the demographc behavour of the populaton, resultng n natural populaton declne, very low fertlty, and wdespread emgraton. Emgraton, especally among ethnc Turks, peaked already at the turn of the 1

2 1980s and 1990, wth a negatve net mgraton estmated at over 470 thousand n the perod (Councl of Europe 2006). The Statstcal Offce and the Bulgaran State Statstcal Organzaton were establshed n The Natonal Statstcal Insttute (NSI) was establshed by the Law on Statstcs n Data collecton All statstcal data on populaton and demographc events are processed and dstrbuted through the NSI. Data on brths are provded by the Unfed System for Cvl Regstraton and Admnstratve Servces of Populaton (thereafter referred to as the cvl regstraton system ). An offcal document certfcate of brth s ssued for each brth. The document ncludes nformaton about the newborn chld, about the mother, and about the father (f he s known), rrespectve of ther martal status. 1.3 Terrtoral coverage There were no terrtoral changes n Bulgara durng the perod covered by the data provded for the Human Fertlty Database (snce 1947). The man category used n the current demographc statstcs and populaton censuses s resdent populaton. Ths category ncludes all the people who resde permanently n the country and have not left t offcally as of December 31 of the respectve year, for a perod of more than one year. Foregn ctzens who stayed n Bulgara for less than a year are not ncluded n the resdent populaton. The aggregate number of lve brths ncludes lve-born chldren who are Bulgaran ctzens, as well as those whose prmary place of resdence s Bulgara, rrespectve of the country of brth. 2 Brth count data Brth data ncluded n the Human Fertlty Database refer to the perod spannng Data for brths n are taken from the offcal demographc publcatons. For the order-specfc data nclude stllbrths and thus are avalable for total brths only. Data on lve brths n ths perod are avalable only by the age-group of the mother, wthout nformaton on brth order. In , lve brths were not regstered by age of the mother at all, and only total numbers of lve brths are avalable for these years (see the fle wth monthly data). For the perod spannng , the data on (lve) brths are classfed by mother s age group and brth order up to 9+. Startng n 1986, the data were extracted from the Informaton System Demography database (ISD) establshed at the NSI on the bass of ndvdual brth records. All the data are specfed by sngle years of age, brth cohort of the mother, and brth order; brth orders up to 11+ are dstngushed. Data on lve brths by months cover the years 1900, 1905, 1910, 1920, 1925, 1930 and 1935, and the perod

3 3 Populaton count data 3.1 Populaton count data by age The annual age structure of women snce 1947 s taken from the Human Mortalty Database (HMD). The data from the HMD for dffer from offcal data of the NSI, as they are adjusted for underestmaton of mgraton and mortalty n nter-censal perods (for reference, see the fle About mortalty data for Bulgara, Phlpov and Jaslons 2002). The dfference n the exposure causes the gap between the offcal TFR and that computed by the HFD of about n Populaton count data by age and party The dstrbuton of the female populaton by age and the number of lve-born chldren s currently avalable from the 2001 census only. These data are tabulated by sngle years of age and number of lve-born chldren up to party fve and hgher. Smlar data were also collected n the 1985 census, but the results were not publshed and thus are not avalable. The 1992 census dd not collect nformaton on the number of lve-born chldren. 4 Specfc detals 4.1 Defnton of lve brth A lve-born chld weghs at least 1,000 or more grams, and shows sgns of lfe (breathng, functonng of the heart, pulsaton of the umblcal cord or voluntary movement of the muscles) after the completon of a pregnancy, rrespectve of ts duraton. If the foetus weghs less than 1,000 grams, t s consdered lve-born only f t survves for at least sx days. A chld s classfed as stllborn f t shows no sgns of lfe, f t s 35 or more centmetres long at the completon of the pregnancy, or f the duraton of pregnancy was at least 28 weeks. Ths defnton was adopted n 1970, and dffers from the WHO recommendatons. Some of the brths that would be consdered lve brths or stllbrths n other countres may therefore be recorded as mscarrages n Bulgara. For extensve dscusson of ths problem see Phlpov and Jaslons In the data were publshed for total brths,.e. nclude stllbrths. For HFD purposes, numbers of lve brths for ths perod were estmated usng the method descrbed n Appendx Age Data on brths by age of the mother refer to age n completed years. Data for are only by 5-year age groups, ncludng the broad age group 19. Snce such a broad age group cannot be satsfactorly recalculated nto sngle years of age usng the present HFD methodology (see the HFD Methods Protocol), data were frst recalculated nto narrower age groups and usng the method descrbed n Appendx 3. Data for (for all brth orders combned) and for (both by brth order and for all brth orders combned) are specfed by Lexs trangles,.e. by both age of mother and mother s brth cohort. However for some years n the schedule of brths by Lexs trangles resemble the zg-zag pattern, ndcatng a possble wrong allocaton of small proporton of brths (up to 2%) nto wrong Lexs trangle. Snce t was not found that the pattern of error s systematc, the HFD nevertheless uses the orgnal data by trangles (whch also conform to Eurostat database data). 3

4 4.3 Brth order Brth order s defned by the total number of lve-born chldren a woman has prevously delvered, wthout countng stllbrths. In case of multple delveres, each chld born s assgned a separate brth order. 4.4 Unknown cases The number of cases wth unknown age of the mother and/or unknown brth order of the chld vares durng the perod covered. In , the number of unknown cases was gradually decreasng from about 300 to less than 100 a year. In , only a very few cases wth unknown age of the mother were recorded, and there were practcally no cases wth unknown brth order of the chld. For foundlngs (abandoned chldren) whose mother was unknown, the age of the mother was mputed as 17 and the brth order was set to one. No unknown cases were recorded n Snce 2000, brths to Bulgaran resdents lvng abroad have been recorded as brths of unknown brth order. The number of brths wth unknown brth order has rsen snce 2007, when Bulgara entered the European Unon and the number of Bulgaran women lvng and bearng chldren abroad ncreased substantally. Whle between 2000 and 2006 there were only about cases wth unknown brth order per year, n 2007 they were 680, n , and n In , the order-specfc data classfed by 5-year age groups nclude a category of unknown age, whle the non-order specfc data classfed by sngle age groups do not have such a category. Ths leads to a slght dsagreement between the totals by 5-year age groups from the both sources. However, the dfferences are very small. 4.5 Specfc detals There are dfferent subpopulatons n Bulgara wth dstnct fertlty behavour. Women wth three and more chldren are manly of Roma ethncty, who begn ther reproducton at a young age. The recent postponement of brths s much more prevalent among Bulgaran women than among Turks and Roma (Koytcheva and Phlpov 2008). Ths can explan why the mean age at second chldbrth has exceeded that of the thrd one n In ths year, the peak age for thrd brth rates was at age 21-23, whle the peak n second brth rates was reached at age Qualty of the data The cvl regstraton system covers n detal all newborn chldren n the country, as well as brths to Bulgaran resdents temporarly lvng abroad. The data are consdered to have a hgh degree of relablty and completeness. The data go through formal and logcal tests, both n the Natonal Cvl Regstraton System and at the Natonal Statstcal Insttute (Informaton System Demography, ISD). Qualty checks are made for each record, and ndvdual regstratons of brths are compared wth the populaton numbers recorded n the ISD. In cases where the data need to be corrected, brth certfcates are used. The brth certfcate s an offcal document of the cvl regstraton system and has legal value. The qualty of populaton data s affected by hgh and undocumented mgraton n the perod after In 1989 and 1990 about 300,000 persons left the country, and around 200,000 returned durng the next 2-3 years. Hgh emgraton contnued nto the 1990s and even ntensfed after 2007, when Bulgara entered the European Unon. These 4

5 ssues are also dscussed n the country documentaton for Bulgara n the Human Mortalty Database (Phlpov and Jaslons 2002). Due to the problems n matchng occurrences (lve brths) wth exposures (female populaton), and lower qualty of the data pror to 1986, cohort data may reach mplausble results. For nstance, chldlessness among the cohorts s lower than 5% and fluctuatng between cohorts. Even though the 2001 census results show very low chldlessness of 4-6% for the cohorts (Koytcheva and Phlpov 2008), the HFD computatons show yet lower, and often mplausble, values (see Fgure 1). Fgure 1: Chldlessness of cohorts as at 2001, accordng to HFD data and census data Even more problematc are the data for hgher partes. As shown n Fgure 2, a comparson of the HFD results derved from vtal statstcs data wth the results recorded n the census of 2001 dscloses huge dfferences between these two sources. Whle the cumulaton of vtal statstcs data used n the HFD computatons underestmates the proporton of women wth one and two chldren, t overestmates the proporton wth three and more chldren. Ths error s partcularly evdent for older cohorts. We attrbute ths dfference to the low qualty of data before 1986 (.e., affectng the cohorts born before 1971) and also to the hgh emgraton pror to the 2001 census. Cohort fertlty ndcators should therefore be used wth extreme cauton, especally for cohorts born before

6 Fgure 2: Proporton of women wth 1, 2 or 3+ chldren by cohort as at 2001, accordng to HFD data and census data For 1987, the total number of lve brths based on age- and brth order-specfc data s by 1 case hgher than the sum of monthly brth data; for 1990, the total number of lve brths based on age- and brth order-specfc data s by 2 cases hgher than the sum of monthly brth data. The reasons for these dscrepances have not been dentfed. 6

7 Data sources 1. Demographc Yearbook of Bulgara ( ). Sofa: NSI. 2. Informaton System Demography database (ISD) Indvdual brth records of NSI. 3. Populaton census n Bulgara Sofa: NSI. 4. Data provded by the Observatore Démographque Européen, who obtaned them n 1983 from the Commttee for ntegrated socal nformaton system to the Councl of Mnsters of Bulgara References Councl of Europe Recent demographc developments n Europe European Populaton Commttee of the Councl of Europe Phlpov, D. and D. Jaslons About mortalty data for Bulgara. Documentaton report for the Human Mortalty Database (updated 2 December 2010). Avalable onlne on Koytcheva, E. and D. Phlpov Bulgara: Ethnc dfferentals n rapdly declnng fertlty. Demographc Research, Vol. 19 (13): Avalable onlne on 7

8 APPENDIX 1 DESCRIPTION OF DATA USED FOR LEXIS DATABASE BULGARIA BIRTHS Perod Type of data Age range Brth order RefCode(s) Annual number of total brths by age of mother and brth order (Lexs squares) , Annual number of lve brths by age of mother (Lexs squares) Annual number of lve brths by age of mother and brth order (Lexs squares) Annual number of lve brths by age of mother (Lexs squares) Annual number of lve brths by age of mother and mother s year of brth (Lexs trangles) Annual number of lve brths by age of mother, mother s year of brth, and brth order (Lexs trangles) Annual number of lve brths by age of mother, mother s year of brth, and brth order (Lexs trangles) 1900, 1905, 1910, 1920, 1925, 1930, 1935, , 20-24,, 40-44, 45+, unknown 1, 2,, 8, 9+, unknown -19, 20-24,, 40-44, 45+, unknown 1-14, 15-19,, 45-49, 1, 2,, 8, 9+, 1 50+, unknown unknown -14, 15,, 49, ,, 49, 50+, unknown 1 10,, 50, 51+, unknown 10,, 50, 51+, unknown 1, 2,, 5, 6+, unknown 1, 2,, 10, 11+, unknown Annual number of lve brths by month FEMALE POPULATION: Dstrbuton by age and party Perod Type of data Age range Year of brth, Party RefCode(s) range Number of women by age and party 0,, 99, , 1, 2, 3, 4, 5+ 3 FEMALE POPULATION: Exposure by age and year of brth Female exposure populaton by calendar year, age and year of brth (Lexs trangles) s estmated usng data on populaton sze and deaths from the Human Mortalty Database, whch s avalable at or 8

9 APPENDIX 2 ADJUSTMENT OF ALL BIRTHS TO LIVE BIRTHS For the years , brth counts by age of the mother and brth order are avalable only for all brths, ncludng stllbrths. However, for the years and , the total number of lve brths n each age category s avalable, and for the years , the total annual number of lve brths s avalable. Snce the lkelhood of stllbrths may vary wth age, for the years where the number of lve brths by age category s avalable, an age- and perod-specfc calculaton was performed to estmate the number of lve brths at each brth order. For the years where only the total number of lve brths s avalable, a perod-specfc calculaton was performed. Note that both calculatons may result n a non-nteger estmate of the number of lve brths by age. Age- and perod-specfc calculaton In order to produce an estmate of the number of lve brths by age and brth order B for the years for whch both lve brths B and total brths B A are avalable by age of the mother, we make a two-step computaton. Frst, we calculate the rato of lve brths to total brths for a gven age and year r (formula 1). Then we multply the counts of total brths specfc for age and brth order n the gven year by ths rato (formula 2). B A B( x, r( x, = A B B A = r( x, B (1) (2) Perod-specfc calculaton In order to estmate the number of lve brths by age and brth order B for the years for whch only total (n respect to brth order) counts of both lve brths B ( and total brths B A ( are avalable, we perform a smlar procedure. We calculate the rato of lve brths to total brths for a gven year r ( and then we multply the counts of total brths specfc for age and brth order n ths year by the estmated rato (formulae 3 and 4). B A B( r( = A B ( B A = r( B (3) (4) 1 In 1954 the recorded number of lve brths wth unknown age of mother (313) s hgher than the recorded number of total brths (.e. ncludng stllbrths) wth unknown age of mother (280), resultng n r(unk,1954)>1. The reason of ths dscrepancy s unknown. HFD uses the frst fgure (313). 9

10 APPENDIX 3 ADJUSTMENTS OF AGE CATEGORY 19 For the years , brth counts by age and brth order are avalable only for the age category 19. Because such a broad age group cannot be satsfactorly recalculated nto sngle age groups usng the HFD methodology (see the HFD Methods Protocol), the data are splt nto two age ntervals and usng a smple method descrbed below. Frst, the rato of brths n the age nterval to brths n the age nterval s estmated for each brth order usng the known values for the years : B ( x 14, t = ) r (12 x 14) =, for = 1, 2 (5) B ( x 19, t = ) r ( 12 x 14) = 0, for = 3, 4, 5+, UNK (6) The obtaned values used n the further calculatons are r (12 x 14) 0.76% and r (12 x 14) 0.08%. 2 = 1 = Then the number of lve brths n the age nterval for each year of the perod and each brth order s estmated as: B ( 12 x 14, = r (12 x 14) B ( x 19, (7) The remanng brths from the age nterval 19 belong to the age nterval