The Turkish Demographic and Health Survey 1998 is the second survey of its kind to be conducted in Turkey after the 1st one in 1993.
The 1998 Turkish Demographic and Health Survey (TDHS-98) is a nationally representative sample survey designed to provide information on fertility levels and trends, infant and child mortality, family planning, and maternal and child health. Survey results are presented at the national level, by urban and rural residence and for each of the five regions in the country.
The survey was fielded between August and November 1998. Hacettepe University Institute of Population Studies (HIPS) carried out the TDHS-98 in collaboration with the General Directorate of Mother and Child Health and Family Planning, Ministry of Health. Funding for the TDHS-98 was provided both by the U.S. Agency for International Development through the MEASURE/DHS+ program and United Nations Population Fund.
Interviews were carried out in 8,059 households, with 8,576 women, and with 1,971 husbands. All women at ages 15-49 who were present in the household on the night before the interview or who generally live in that household were eligible for the survey. In half of the selected households for women interview, husbands (of currently married eligible women), who were present in the household on the night before the interview or who generally live in that particular household were eligible husbands for the survey.
The 1998 Turkish Demographic and Health Survey (TDHS-98) is the latest in a series of national- level population and health surveys that have been conducted during the last thirty years in Turkey. The primary objective of the TDHS-98 is to provide data on fertility and mortality, family planning, materaal and child health, and reproductive health. The survey obtained detailed information on these issues from a sample of women in the reproductive ages (15-49) and from fl~e husbands of cun'ently married eligible women.
More specifically, the objectives of the TDHS were to:
- Collect data at the national level that allow the calculation of demographic rates, particularly fertility and childhood mortality rates;
Obtain information on direct and indirect factors that determine levels and trends in fertility and childhood mortality;
- Measure the level of contraceptive knowledge and practice by method, region, and urban- rural residence;
- Collect data on mother and child health, including innnunisations, prevalence and treatment of diarrhoea among children under five, antenatal care, assistance at delivery, and breastfeeding;
- Measure the nutritional status of children under five and of their mothers using anthropometric measurements.
Kind of Data
Sample survey data
Unit of Analysis
- Women age 15-49
- Children under five
The Turkish Demographic and Health Survey 1998 covers the following topics:
- Fertility preferences
- HIV Knowledge-Questions assess knowledge/sources of knowledge/ways to avoid HIV
- Husband's background
- Immunisation and health
- Maternal care and breastfeeding
- Materal and child anthropometry
- Men's Survey
- Reproductive Calendar
- Social Marketing
- Tobacco Use
- Women's Status–Questions: women's autonomy (household decisionmaking/free movement/access money) & Dom. violence
The 1998 Turkish Demographic and Health Survey (TDHS-98) is a nationally representative sample survey. Results are also presented by urban and rural residence and for each of the five regions in the country (West, South, Central, North and East).
The population covered by the 1998 DHS is defined as the universe of all women at ages 15-49 who were present in the household on the night before the interview were eligible for the survey. In half of the selected households for women interview, husbands of currently married eligible women, who were present in the household on the night before the interview or who usually lived in the household were eligible for the husband survey.
Producers and sponsors
Institute of Population Studies
General Directorate of Mother and Child Health and Family Planning
Ministry of Health
Macro International Inc.
U.S. Agency for International Development
United Nations Population Fund
The sample for tile TDHS-98 was designed to provide estimates of population and health indicators including fertility and mortality rates for the nation as a who/e, for urban and rural areas, and for tile five major regions of tile country (West, South, Central, North and East). A weighted, multi-stage, stratified cluster sampling approach was used in tile selection of the TDHS-98 sample.
The optimal distribution with a target sample size of I0,000 selected households was based on the provisional results of the 1997 General Population Count. Selection of the TDHS-98 sample was undertaken in three stages. Tile sampling units at tile first stage were tile settlements stratified by population size. The ti'ame for the selection of the primary sampling units (PSU) was prepared using the provisional results of the 1997 Population Count. The fi'ame was divided into two groups, one including those settlements with populations of more than 10,000 and the other including settlements with populations less than 10,000. The selection of the settlement in each group was carried out with probability proportional to size (1997 poptdatiou).
The second stage of selection required the selection of the assigned nnmber of clusters in each selected settlement. For the majority of the settlements (340 clusters), the selection of clusters was based on the household lists that were available from the 1995 Structure Schedules. The State Institute of Statistics (SIS) selected the clusters and provided to Hacettepe Institute of Population Studies a description of each selected cluster. Each cluster included approximately 100 households. For those settlements where SIS was not able to provide information (140 clusters), the lists of households were prepared in the field.
Following the selection of the secondary sampling units (SSUs), a household listing was prepared or updated for each SSU by the TDHS-98 listing teams. Using the household lists, a systematic random sample of fixed number of households (25 in clusters located in settlements over 10,000 and 15 in those less than 10,000) was chosen within each cluster for the TDHS-98. All women at ages 15-49 who were present in the household on the night before the interview were eligible for the survey. In half of the selected households for women interview, husbands of currently married eligible women, who were present in the household on the night before the interview or who usually lived in the household were eligible for the husband survey.
Different criteria have been used to describe "urban" and "rural" settlements in Turkey. In the demographic surveys of the 1970s a population size of 2,000 was used to differentiate between urban and rural settlements. In the 1980s, this was increased to 10,00O and, in some surveys in the 1990s, to 20,000. A number of surveys used the administrative status of settlements in combination with population size for the purpose of differentiation.
The urban frame of the 1998 TDHS consisted of a list of provincial centres, district centres, and other settlements with populations larger than 10,000, regardless of administrative status. In turn, the rural frame consists of all district centres, subdistricts and villages not included iF the urban fi'ame. Initial information on these settlements was obtained from the preliminary results of 1997 Population Count. The preliminary results of 1997 Population Count provided a computerized list of all settlements (provincial and district centres, , subdistricts and villages) and their population. The population counts were taken from the cumulative enumeration forms for settlements, which were filled by supervisors during the Population Count.
Currently Turkey is divided administratively into 80 provinces. This figure was 67 for a long time, with new provinces formed since the late 1980s, For purposes of selection in prior surveys in Turkey, these provinces have been grouped into five regions, as described in Chapter 1. This regional breakdown has been popularised as a powerful variable for understanding the demographic, social, cultural, and economic differences between different parts of the country. The five regions, West, South, Central, North, and East regions, include varying numbers of provinces.
One of tile priorities of the TDHS was to produce a sample design that was methodologically and conceptually consistent with the designs of previous demographic surveys carried out by the Hacettepe Institute of Population Studies. In surveys prior to the 1993, the five-region division of the country was used for stratification. In the 1993 TDHS, a more detailed stratification taking into account subregions was employed to obtain a better dispersion of file sample. The criteria for subdividing the five major regions into subregions were the infant mortality rates &each province, estimated from the 1990 Population Census using indirect techniques? Using the infant mortality estimates as well as geographic proximity, the provinces in each region were grouped into 14 subregions at the time of the 1993 TDHS. The sub-regional division developed during the 1993 TDHS was used in the 1998 survey.
The target sample size of 10,000 households was allocated among the five major divisions using the sampling error estimates from the TDHS-93 in combination with the power allocation technique with the ex- pectation that the target sample size would provide about 8,000 completed individual interviews. During the power allocation calculations, the aim was to keep the allocation as similar as possible to the 1993 TDHS. The optimal distribution (with power 0.4) among the five major regions is shown in Table B.I. For purposes of comparison, Table B.I also shows the allocation of the TDHS-93 sample and the allocation if the TDHS-98 sample had been distributed proportional to the size of the population in each region. To have an adequate representation of clusters within each of the five major regions, it was decided to select 25 households per standard urban segments (each consisting of 100 households) and 15 households per standard rural segment. It was also determined that 70 percent of the 10,000 households would be located in urban settlements and 30 percent in rural settlements.
SAMPLE SELECTION - SELECTION PROCEDURES
The lists of settlements of urban settlements (settlements with I 0,000 or more population) and rural settlements (settlements with less than 10,000 population) constituted the frame for the first stage of the sample selection. For tile selection of the first-stage sample, settlements were grouped within each of the 14 subregions, and a systematic random sample of settlements with probability proportional to size (PPS) based on file preliminary 1997 Population Count was selected from the settlement lists. The output from this first stage of the selection was a list of all of the settlements included in the 1998 TDHS sample along with the number of clusters to be drawn from each settlement.
In Turkey, settlements are not divided into small areal units with well-defined boundaries (e.g., census enumeration areas) that can be used for conducting surveys. For some settlements, however, household lists were available from the Structure Schedules that were prepared in 1995 by many municipalities in collaboration with the State Institute of Statistics (SIS). Household lists from the Structure Schedules were available for settlements from which 340 clusters in the TDHS-98 sample were to be drawn. For those settlements, the household lists were subdivided into segments of approximately 100 households. The list of these segments constituted the frame for the selection of the 340 clusters. For each of the selected clusters, SIS provided a list of the dwellings units with their full addresses (quarter, area, avenue/street, building and door number).
SIS was not able to provide a frame from the 1995 Structure Schedules for settlements from which I40 clusters were to be drawn for the TDHS-98. For these settlements, the list of households had to be prepared in file field. In the case of small settlements (less than 250 households), the entire settlement was listed. In the ease of the small number of settlements in which there were more than 250 households, 200 households were listed and an estimate of the remaining number of households in the settlement was obtained through a quick count.
LISTING AND MAPPING ACTIVITIES
Although tile SIS had dwelling lists for many clusters, they did not have the corresponding maps. For this reason, the selected clusters were formed with streets that were not always adjacent to each other. Moreover, the lists provided by the SIS did not reflect changes that may have occurred during the period from the 1995 to tile survey date. Two types of changes were possible: those that could be updated during listing, such as the construction of a new building oil the street, a change in the use of a building (e.g., a fiat can be used as an office instead of a dwelling), or changes in the names of streets, and those that were more problematic, e.g., the appearance of new quarters in urban centres.
In an effort to develop strategies for dealing with these as well as other possible problems that might arise, a pilot listing activity was undertaken in the capital, Ankara, before the actual listing activity began. The final listing forms, sketch map formats, and listing and mapping manuals were developed based on this experience.
Forty (40) university students were trained for the main listing activity. Listing teams were formed following a four-day training program in the beginning of June 1998. Each team was provided with maps describing the location of the settlements they were expected to visit as well as other materials needed for the listing. Sixteenth (16) listing teams were constituted" with" one mapper and one lister. The listing operation started on 8 of June. It was carried under the supervision of the research assistants and regional coordinators from the Hacettepe Institute of Population Studies.
The cluster (standard segment) size was around 100 households for most of the clusters in urban areas. Only two urban clusters had extremely low numbers of households; in order to obtain 100 households in these clusters, adjacent streets were added to the original cluster. In some of the selected villages, the total populations also were small, and, therefore, the original cluster did not include 100 households. In these cases, the village that was nearest to the selected village was included in the sample, and the names of these villages were provided to the listing teams; the lists of 100 households were completed from the two villages.
Most of the listing activity was completed before the training for the main fieldwork began in July. Overall, the quality of the listing work produced by the listers was good although it varied somewhat largely in response to problems the listing teams experienced in working in some geographic areas. In particular, there were some problems with the listing of clusters of Adana province where there had been an earthquake. There also were problems with the lists for Içel province. Finally, three clusters were not listed due to problems of accessibility.
In all, 9,970 households were selected for the TDHS-98. At the time of the survey, 8,596 households were considered occupied and, thus, available for interview. The main reasons the field teams were unable to interview some households was because some dwelling units that had been listed were found to be vacant at the time of the interview or the household was away for the extended period. Of tile 8,596 occupied households 94 percent (8,059 households) were successfully interviewed.
In the interviewed households, 9,468 women were identified as eligible for the individual interview, i.e. they were women at reproductive ages (15-49) who were present in the household on the night before the interview. Interviews were successfully completed with 8,576 of these women (91 percent). Among the eligible women not interviewed ill the survey, the principal reason for non-response was the failure to find tile women at home after repeated visits to the household.
In half of the selected households, husbands of currently married eligible women who were present in the household on the night before the interview or who usually lived in that particular household were eligible for the husband survey. A total of 4,983 households were selected for the husband interview. In the households interviewed (4,321 households), 3,043 husbands were identified as eligible for the individual interview. These husbands were present in the household on the night before tile interview and they were currently married to women at reproductive ages. Of the 3,043 husbands designated as eligible for individual interview, 65 percent (1,971) were successfully interviewed.
The TDHS sampling plan is not a self-weighted one. In particular, a disproportionate number of sample units were chosen from the North, East and South regions, since there would have been inadequate numbers of observations for these areas if the target number of households had been proportionally allocated across regions.
Dates of Data Collection
Data Collection Mode
Four regional coordinators were responsible for visiting the fieldwork teams ill turn, checking the quality of data collected, and reporting periodically to the field director in Aukara. Fieldwork teams visited 76 of the 80 provinces in Turkey.
Data Collection Notes
In May 1998, a pre-test was conducted to ensure that the questions in the TDHS questionnaires were in a logical sequence; that the wording of the questions was comprehensible, appropriate and meaningful; and that the precoded answers were adequate.
Nineteen interviewers were trained at the Haeettepe Institute of Population Studies for a period of two weeks. The training period included both classroom training and interviews in the field. The interviewers were mostly university students and graduates. In addition to the interviewers, research assistants, who would later become regional coordinators and supervisors, also received training.
Fieldwork for the pretest was carried out in one district in central Ankara, two districts in squatter housing areas of Ankara, and three villages in Ankara province. A total of 185 household, 172 ever-married women, 72 husband and 45 never-married women interviews were completed during the pretest. Frequency distributions and cross tabulations were obtained shortly atier the completion of the interviews. Based on the evaluation of these results and on the feedback obtained from the interviewers, several minor changes were made to the TDHS questionnaires.
STAFF RECRUITMENT AND TRAINING
Candidates for the positions of interviewers, field editors, supervisors and measurers were solicited in announcements sent to the all universities in Ankara and from the Institute of Population Studies files of field staff who had worked on previous surveys. All candidates for the field staff positions were interviewed in four groups by the staff of the Institute of Population Studies using interview guidelines prepared for this purpose. Individuals who met a number of the requirements and had the necessary qualifications were accepted into the training program.
All candidates for the field staff positions were at least high school graduates and the majority were university students. Previous survey experience was not among the qualifications for the candidates for the position of interviewers in order to ensure that the trainees had no biases that might result from their previous experience. Approximately 120 applicants were accepted for the training program.
Training of the candidates for the fieldwork positions was conducted in July 1998 for three weeks at the Hacettepe Institute of Population Studies. The training program included general lectures related to the demographic situation in Turkey, family planning and mother and child health, questionnaire training, role playing and mock interviews, field practice in areas not covered in the survey and quizzes to test the progress and capabilities of the candidates. A variety of materials were used during the training sessions, including manuals for supervisors and editors, and for interviewers.
All trainees received the same classroom training during the first two weeks of the training period; at the end of the third week, supervisors, field editors, and measurers were selected from among the candidates, and a number of unsuccessful candidates were eliminated at this stage. Separate classroom training sessions were organized for supervisors, field editors, and measurers.
Fieldwork for the TDHS, including initial interviews, callbacks and reinterviews began in the first week of August 1998 and was completed at the end of November 1998.
Fieldwork activities were completed in two stages. In the first stage, data collection was carried out by 12 teams, each consisting of a supervisor, a field editor, and 4 or 5 female and one male interviewers, depending on the workload of that specific team. The male interviewer and field editor worked as measurers as well. The first stage of the fieldwork was completed by the end of September, at which point a number of fieldwork staff, as agreed initially, discontinued working in the field. Four new teams were set up from among the staff of the 12 teams that had worked in the first stage of fieldwork. The teams at this second stage had the sarae composition as those in the first stage. These teams continued with data collection activities until the end of November.
Four regional coordinators were responsible for visiting the fieldwork teams ill turn, checking the quality of data collected, and reporting periodically to the field director in Aukara.
Fieldwork teams visited 76 of the 80 provinces in Turkey. The TDHS fieldwork was a relatively rapid operation because of the specific conditions prevailing in the country, i.e., a large proportion office fieldwork staff consisted of students who had to begin school in October and climatic conditions in many parts of the country limited access after October.
A total of 480 clusters were selected for the TDHS sample. Of these, interviews were successfully completed in 476 clusters. Due to problems of access and lack of security, three clusters were not listed and, consequently, were not visited by the fieldwork teams; in addition, a cluster that had been listed could not be visited by the fieldwork teams.
Hacettepe Institute of Population Studies
Four main types of questionnaires were used in the TDHS-98: the Household Questionnaire and three Individual Questionnaires, one for ever-married women of reproductive ages, one for never-married women, and one for husbands. The contents of the questionnaires were based on the DHS Model 'A' Questionnaire, which was designed for the DHS program for use in countries with high contraceptive prevalence Additions, deletions and modifications were made to the model questionnaire in order to collect information partictdarly relevant to Turkey. In developing the questionnaire, close attention was paid to obtaining the data needed for program planning in Turkey as specified during eousultations with population and health agencies. Ensuring the comparability of the TDHS-98 findings with previous demographic surveys carried out by the Hacettepe Institute of Population Studies also was a goal during questionnaire development. The questionnaires were developed in English and translated into Turkish.
a) The Household Questionnaire was used to enumerate all usual members of and visitors to tile selected households and to collect information relating to the socioeconomic situation of the households. In the first part of the household questionnaire, basic information was collected on the age, sex, educational attainment, marital status and relationship to the head of household of each person listed as a household member or visitor. The objective of the first part of the Household Questionnaire was to obtain the information needed to identify women and husbands who were eligible for the individual interview as well as to provide basic demographic data for Turkish households. The second part of the Household Questionnaire included questions on the welfare of the aged people, lu the third part of the Household Questionnaire, questions were included on tile dwelling unit, such as the nulnber of rooms, the flooring material, the source of water, and the type of toilet facilities, and on the household's ownership of a variety of consumer goods.
b) The Individual Questionnaire for women I covered the following major topics:
- Background characteristics
- Knowledge and use of falmily planning
- Maternal care and breastfeeding
- Other issues relating to contraception
- Immunisation and health
- Fertility preferences
- Husband's background
- Women's work and status
- Sexually transmitted diseases
- AIDS Maternal and child anthropometry.
c) The Individual Questionnaire for ever-married women included a monthly calendar, which was used to record fertility, contraception, marriage and migration histories for a period of approximately six years beginning in January 1993 up to the survey month. In addition, fieldwork teams measured the heights and weights of children under age five and of all women at ages 15-49. The Individual Questionnaire for never-married women covered the following subjects:
- Background characteristics
- Knowledge and use of family planning
- Fertility preferences
- Women's work and status
- Sexually transmitted diseases and AIDS
d) The Individual Questionnaire for husbands covered the following topics:
- Background characteristics
- Knowledge and use of family planning
- Fertility preferences
- Sexually transmitted diseases and AIDS
The questionnaires were returned to the Institute of Population Studies by the fieldwork teams for data processing as soon as interviews were completed in a province. The office editing staff checked that the questionnaires for all the selected households and eligible respondents were returned from the field. The comparatively few questions that had not been precoded (e.g., occupation) were coded at this time.
The data were entered and edited on microcomputers using tbe Integrated System for Survey Analysis (ISSA), a package program specifically developed to process DHS data. ISSA allows range, skip, and consistency errors to be detected and corrected at the data entry stage. The machine entry and editing activities were initiated within one week after the beginning of the fieldwork and were completed a few days al~er the completion of the fieldwork.
Advantage was taken of the fact that data processing activities ran concurrently with fieldwork. Field check tables fi'om edited data were periodically produced for each interviewing team. These focused on such potential problems as high proportious of incomplete households and displacement of eligible respondents and were used to check the progress and quality of data from the field.
Estimates of Sampling Error
Sampling errors, on the other hand, can be evaluated statistically. The sample &respondents selected in the TDHS is only one of many samples that could have been selected from the same population, using the same design and expected size. Each of these samples would yield results that differ somewhat from the results &the actual sample selected. Sampling errors are a measure of the variability between all possible samples. Although the degree &variability is not known exactly, it can be estimated from the survey results.
A sampling error is usually measured in terms of the standard error for a particular statistic (mean, percentage, etc.), which is the square root of the variance. The standard error can be used to calculate confidence intervals within which the true value for the population can reasonably be assumed to fall. For example, for any given statistic calculated from a sample survey, the value of that statistic will fall within a range of plus or minus two times the standard error of that statistic in 95 percent of all possible samples of identical size and design.
If the sample of respondents had been selected as a simple random sample, it would have been possible to use straightforward formulas for calculating sampling errors. However, the TDHS sample is the result of a three-stage stratified design, and, consequently, it was necessary to use more complex formulae. The computer software used to calculate sampling errors for the TDHS is the 1SSA Sampling Error Module (SAMPERR). This module used the Taylor linearization method of variance estimation for survey estimates that are means or proportions. The Jackknife repeated replication method is used for variance estimation of more complex statistics such as fertility and mortality rates.
The Jackknife repeated replication method derives estimates of complex rates from each of several replications of the parent sample, and calculates standard errors for these estimates using simple formulae. Each replication considers all but one clusters in the calculation of the estimates. Pseudo-Independent replications are thus created. In the TDHS, there were 476 non-empty clusters.
In addition to tile standard error, SAMPERR computes tile design effect (DEFT) for each estimate, which is defined as the ratio between the standard error using the given sample design and the standard error that would result if a simple random sample had been used. A DEFT value of 1.0 indicates that file sample design is as efficient as a simple random sample, while a value greater than 1.0 indicates the increase in the sampling error due to the use of a more complex and less statistically efficient design. SAMPERR also computes the relative error and confidence limits for the estimates.
Sampling errors for tile TDHS are calculated for a number of variables considered to be of primary interest, Results for women and for husbands are presented in an appendix to the Final reportfor the country as a whole, for urban and rural areas, and for each of the five regions: West, South, Central, North and East. For each variable, the type of statistic (mean, proportion, or rate) and the base population are given in Table C.1 of the Final Report. Tables C.2-C.9 present the value of the statistic (R), its standard error (SE), the number of unweighted (N) and weighted (WN) cases, the design effect (DEFT), the relative standard error (SE/R), and the 95 percent confidence limits (R_+2SE), for each variable. The DEFT is considered undefined when the standard error considering simple random sample is zero (when the estimate is close to 0 or 1).
In general, the relative standard errors for most estimates for the country as a whole are small, except for estimates of very small proportions. There are some differentials in the relative standard errors for the estimates for sub-populations. For example, for the contraceptive prevalence rate (CPR), i.e. the proportion of currently married women aged 15-49 who were using any method of contraception at the time of the interview, the relative standard error for the country as a whole, for urban areas, and for rural areas are 1.2 percent, 1.4 percent, and 2.7 percent, respectively. To obtain the 95 percent confidence limits for the CPR, one adds and subtracts twice the standard error to the sample estimate, ie. 0.639 + 2x.007. The results indict that there is a high probability (95 percent) that tile true value of the CPR for the country as a whole lies between 62.3 percent and 65.4 percent.
Nonsampling errors are the results of mistakes made in implementing data collection and data processing, such as failure to locate and interview the correct household, misunderstanding of the questions on the part of either the interviewer or the respondent, and data entry errors. Although numerous efforts were made during the implementation of the TDHS to minimize this type &error, nonsampling errors are impossible to avoid and difficult to evaluate statistically.
Use of the dataset must be acknowledged using a citation which would include:
- the Identification of the Primary Investigator
- the title of the survey (including country, acronym and year of implementation)
- the survey reference number
- the source and date of download
Disclaimer and copyrights
The user of the data acknowledges that the original collector of the data, the authorized distributor of the data, and the relevant funding agency bear no responsibility for use of the data or for interpretations or inferences based upon such uses.