The National Income Dynamics Study (NIDS) is a face-to-face longitudinal survey of individuals living in South Africa as well as their households. The survey was designed to give effect to the dimensions of the well-being of South Africans, to be tracked over time. At the broadest level, these were:
Wealth creation in terms of income and expenditure dynamics and asset endowments;
Demographic dynamics as these relate to household composition and migration;
Social heritage, including education and employment dynamics, the impact of life events (including positive and negative shocks), social capital and intergenerational developments;
Access to cash transfers and social services
Wave 1 of the survey, conducted in 2008, collected the detailed information for the national sample.
Wave 2 of NIDS re-interviewed respondents interviewed in Wave 1, gathering information on developments in their lives since they were interviewed in 2008.
Wave 3 of the survey took place between April and December 2012 and re-interviewed respondents from Waves 1 and 2.
Completed and non-response interviews in the NIDS data:
The NIDS datasets contain both completed and non-response interviews (e.g. Refusals). It is recommended that researchers limit their research to completed interviews to avoid item non-response from non-response interviews. The completed interviews can be identified by making use of the w`x'_`y'_outcome variables, where `x' represents the wave and `y' represents the relevant data file/outcome type indicator. These outcome variables can be found in each of the following data files, Adult, Child, Proxy, HHQuestionnaire and Link File.
The only exception to this is Wave 1 where no outcome variable exists. This is because at a household level, all of the interviews are completed. However this does not apply at an individual level where non-response interviews can be identified by making use of the "Reason for refusal" variables, namely w1_a_refexpl or w1_c_refexpl in the Adult and Child data files respectively.
Kind of Data
Sample survey data [ssd]
Unit of Analysis
The units of analysis in the survey are individuals and households.
The NIDS questionnaires attempted to gather information on all members of the household; including those that were resident and those that were non-resident at the time of the interview. Those that were resident provided the base sample of individuals who will remain in the NIDS sample over time. Information about non-resident members is essential in understanding the household and family support systems that individuals have around them at the time of the interview.
v3.0.0: Edited, anonymised dataset for public distribution.
This explains changes in any new versions of the data. Note that the version numbers for the latest versions of NIDS have not been updated in the do files in the program library that has been made available to assist researchers with data manipulation. Data users should update the global to the version of the data they are using.
CHANGES IN NIDS WAVE 3 2012 DATA FROM VERSION V1.0 TO VERSION V1.1
Admin data has been created for the first time for the Wave 3 data. As is the now the case in Wave 1 and 2 it is part of the regular wave specific pack. We hope that this convenience will enrich users' experience of developing research from this ever growing resource. The publically available data matches the names of schools as collected by NIDS to Department of Basic Education's Ordinary School's Master List. Only a limited number of variables are made publically available to protect the identities of NIDS respondents. A secure data facility is provided where researchers can match their own data sources based on EMIS numbers to the matched schools. See <http://www.nids.uct.ac.za/nids-data/secure-data> for further details.
In the last release, the best estimate for agriculture income w3_hhagric was calculated using two variables from the Adult questionnaire which are w3_a_empsll_v and w3_a_empconprod_v. In this release, income from agriculture activities is calculated using variables from the HHQuestionnaire file. The process used in the calculation for agriculture income in wave 3 is now similar to the process used in wave 1. See program library files on <http://www.nids.uct.ac.za/documents/program-library/151-wave-3-income-dofiles> for details on how agriculture income was calculated.
The variable w3_a_wncom which was incorrectly named in the Adult file in the last release has been renamed back to w3_a_owncom.
Birth History Section
In the Adult file there a few individual males who were listed as having given birth in variable w3_a_bhbrth. This error has now been rectified as it is impossible for males to give birth.
Non-Residents in the Link File
There were 53 records where individuals who were non-resident in Wave 1 were assigned a Wave 1 household identifier (w1_hhid) in the Wave 3 Link File. This has been corrected to ensure that no non-resident members have household identifier in the Link File in the waves that they are non-resident.
Through interaction with our users it was brought to our attention that the svyset command in STATA was retaining settings. We have subsequently removed these settings from all data sets.
CHANGES IN W3 FROM V1.1 TO V1.2
NIDS datasets have been reweighted to take into account the Census 2011 geographic data. Both the household level, as well as the individual level panel weights has been adjusted.
Previous geographic variables have been given the suffix ‘2001’ to distinguish them from the new geographic variables. The following variables were affected:
Old Variable Name New Variable Name
*Secure dataset variables
Census 2011 Geographic Variables have been brought into the NIDS dataset. The new variables are:
New Variable Name w3_gc_prov2011 w3_gc_dc2011 w3_gc_mdbdc2011 w3_hhgeo2011 w3_gc_eatype2011* w3_gc_ea2011* w3_gc_mp2011* w3_mapped_prov2011* w3_mapped_dc2011* w3_mapped_mdbdc2011* w3_mapped_mp2011* w3_mapped_geo2011* w3_mapped_ea2011* w3_mapped_eatype2011
*Secure dataset variables
More detail about this change can be found in the document detailing the Inclusion of Census 2011 data in NIDS.
Household Questionnaire for NIDS Wave 3 2012
The final version of the household questionnaire issued with the NIDS Wave 3 2012 Public Use Files had the codes for DECEASED and ABSENT in questions b18, b19 and b20 transposed from the original questionnaire used in data collection. This has been corrected in version 1.1 of this questionnaire (W3_hh_final-v1.1)
This version of the dataset included a syntax file to correct two variables in NIDS Wave 3 2012 Adult, Child and Proxy data files. These variables were incorrectly coded for instances where the response should be '10: Out of the Country'. The variables are:
Province Respondent Born In (Question B11_3 (w3_a_brnprov), B7_3 (w3_c_brnprov), and B9_3 (w3_p_brnprov), in the Wave 3 Adult, Child and Proxy questionnaires respectively)
Province Before Current Location (Question B16_3 (w3_a_lvbfprov), B11_3 (w3_c_lvbfprov), and B14_3 (w3_p_lvbfprov), in the Wave 3 Adult, Child and Proxy questionnaires respectively)
CHANGES IN W3 FROM VERSION 1.2 TO VERSION 1.3
This change relates to the following variables in the Wave 3 NIDS Adult data file.
· w3_a_emssect - E34.1 (Self-employment sector code),
· w3_a_emsothsect - E36.1 (Other self-employment sector code) and
· w3_a_emcprod_c - E49.1 (Casual employment sector codes
In all three cases the variables were inconsistently coded for the sectors: In previous waves the codes matched for the sectors highlighted below. Version 1.2 of Wave 3 had non-matching codes. These have been changed in version 1.3 to match codes for sectors by employment type, as in previous waves.
In addition to the above, the variable name w3_a_emcprod_c was incorrectly assigned to E49.1. The correct variable name is w3_a_emcsect.
This change relates to the following variables in the Wave 3 NIDS Adult, Child and Proxy datasets:
· Province Respondent Born In (Question B11_3 (w3_a_brnprov), B7_3 (w3_c_brnprov), and B9_3 (w3_p_brnprov), in the Wave 3 Adult, Child and Proxy questionnaires respectively)
· Province Before Current Location (Question B16_3 (w3_a_lvbfprov), B11_3 (w3_c_lvbfprov), and B14_3 (w3_p_lvbfprov), in the Wave 3 Adult, Child and Proxy questionnaires respectively)
In both cases the variables were incorrectly coded for instances where the response should be '10: Out of the Country'. This has now been corrected.
CHANGES IN W3 FROM VERSION 1.3 TO VERSION 2
New Variables/Info in version 3
In the Adult, Child and Proxy questionnaires NIDS gathers information regarding all the locations in which respondents have lived (Questions b10 - b16 in the adult questionnaire). These questions are collectively known as migration questions. In previous releases this data has only been coded using 2001 Census data to district municipality level (DC). In the latest release the data has been coded to both the 2001 and 2011 Census data, and with both versions of the district municipality codes. New variables for migration have the suffix dc_2001 and dc_2011 for descriptions coded to the 2001 and 2011 Census data respectively.
Birth History Section
NIDS embarked on an exercise to identify and match all the children across Wave 1 - Wave 4 on Birth History (BH). In cleaning this section, NIDS made calls to confirm the number of children the mother had given birth to. Therefore there were a lot of changes to this section because some children were either added or dropped in the mother's birth history. An additional gain from this exercise is that each child in the BH section now has a PID to identify them.
Police District data
Police district data has now been included as part of the Admin data file. Variables include distance to the nearest police station, and distance to the police station in the district in which the household is located. Only categorical distances have been included in the public release version of the data. Actual distances can be found in the secure (restricted access) version of the data.
An exercise to reduce inconsistences in the parental information was carried out for all individuals across all waves. Cases with problems were identified by comparing parental information across waves. In cases where the information varied across waves, calls were made to verify this information. Information obtained from the calls was used to correct the inconsistent parental data. Where respondents could not be contacted, the data remain unchanged.
The variable w3_pweightw2w3 was dropped from the indderived file. This was done for two reasons.
1. The number of weights to be calculated across waves increases exponentially with each wave. Researchers wishing to use the variablevcan use the method described in the Panel User Guide to calculate the weights.
2. The interpretation of this type of weight is very complex.
A list of all variables renamed in the new versions of the datasets can be found in the document "nids-w3-2012-changes" included in the dataset.
CHANGES IN VERSION 2.1
Version 2.1 had changes to the weights variables, w3_pweight in the indderived data file and the w3_wgt in the hhderived data file. Changes to these variables were necessary because:
1.Panel weights were missing for some babies born to CSM mothers after Wave 1 (2008)
2. The weight was missing for one (now adult) respondent
3. This version includes a syntax file to correct an error concerning the w*_a_unemwnt (number of years wanting work with no success) variable in the Adult data file. This variable was inconsistently re-named across the panel. This variable name will be corrected in the next NIDS data release.
CHANGES IN VERSION 3.0.0
Version 3.0.0 of NIDS wave 3 includes changes to the number of individuals and households in each data file, largely driven by previously incorrect classification of TSM/CSM status, duplicate interviews and additional baby CSMs not captured in a previous version of this wave. Version 3.0.0 also contains new and renamed variables, and there are changes to the survey weights. For details on these changes please see the document Wave 3 Changes between V2.1 and V3.0.0 which is provided with the data.
Data on the following topics was collected during the survey:
HOUSEHOLD: Household characteristics, household roster, mortality history, living standards, expenditure, consumption, negative events, positive events, agriculture
ADULTS: Demographics, education, labour market participation, income, health, well-being, numeracy, anthropometric data
CHILDREN: Education, health, family support, grants, anthropometric data, numeracy
The NIDS data is nationally representative. The survey began in 2008 with a nationally representative sample of over 28,000 individuals in 7,300 households across the country. The survey is repeated every two years with these same household members, who are called Continuing Sample Members (CSMs). The survey is designed to follow people who are CSMs, wherever they may be in SA at the time of interview. The NIDS data is therefore, by design, not representative provincially or at a lower level of geography (e.g. District Council).
The lowest level of geographic aggregation in the NIDS public release data is District Municipality. However, the data is not representative at any level but the national level. Data that includes household-level geo-coding is available for use in DataFirst's Secure Centre at the University of Cape Town.
The target population for NIDS was private households in all nine provinces of South Africa, and residents in workers' hostels, convents and monasteries. The frame excludes other collective living quarters, such as student hostels, old age homes, hospitals, prisons and military barracks.
Producers and sponsors
Southern Africa Labour and Development Research Unit
University of Cape Town
Government of South Africa
Dates of Data Collection
Data Collection Mode
Data Collection Notes
Fieldwork for NIDS Wave 3 commenced in April 2012 and was concluded in December 2012.
Questionnaire Section 3: Food expenditure and consumption data:
NIDS collected data on total food expenditure of the household. The questions used to collect food consumption data were:
E1.1 What was the total food expenditure of this household in the last 30 days? (variablename fdtot)
E1.2 Would you say the total food expenditure for this household in the last 30 days was (fdtot_brac1-6)
E1.3a Did you receive any foodstuffs as payment in the last 30 days? (fdrec)
E1.3b Did you produce/grow/gather any foodstuffs in the past 30 days? (fdprd)
E1.3c Did you consume any foodstuffs in the past 30 days out of your own shop stock? (fdcon)
In NIDS Wave 1 (2008) and Wave 2 (2010-2011) enumerators asked these questions and questions on detailed food expenditure and consumption. From Wave 3 (2012) onwards, if the total food expenditure data was deemed to be accurate based on computer checks, enumerators skipped past the detailed food consumption questions. Therefore, from Wave 3 detailed food consumption variables will not be included in the household data file. Data users are advised to read the questionnaire for more detail on the skip patterns in this section.
Questionnaire Section 7 Question S7: Private Security of Household:
The Interviewer Evaluation Section of the NIDS Household questionnaire (Section 7) has a question (S7) on the level/type of private security on the HH premises. This assessment is made by the interviewer. Data from the Interviewer Evaluation Section (Section 7) of the questionnaire was not released in Wave 1 (2008) and Wave 2 (2010-2011). From Wave 3 (2012) an anonymised version of the evaluation data has been made available in the NIDS public release.However, private security of HH data collected with question S7 was excluded and is not available in the NIDS public release data or secure data as it doesn't fall within the scope of NIDS respondent consent.
Registering to use the NIDS data includes agreement that the data user will not attempt to identify specific individuals from the data.
Public use data, available to all
Southern Africa Labour and Development Research Unit. National Income Dynamics Study Wave 3, 2012 [dataset]. Version 3.0.0. Pretoria: SA Presidency [funding agency]. Cape Town: Southern Africa Labour and Development Research Unit [implementer], 2016. Cape Town: DataFirst [distributor], 2016. DOI: https://doi.org/10.25828/7pgq-q106