1. What is NIDS and when did it start?
The National Income Dynamics Study (NIDS) is the first national panel study in South Africa. The Southern Africa Labour and Development Research Unit (SALDRU) based in the School of Economics at the University of Cape Town is tasked with implementing this survey. The study began in 2008 with a nationally representative sample of over 28,000 individuals in approximately 7,300 households across the country. The survey continues to be repeated with these same household members every two years and examines the livelihoods of individuals and households over time.
2. What makes NIDS different?
The National Income Dynamics Study (NIDS) is the first national panel study in South Africa. As the panel unfolds, it will reveal the dynamic structure of households in South Africa, changes in the living conditions and well-being of household members in a way that no other study in South Africa has been able to do thus far. A key feature of the study is its ability to follow people as they move out of their original households.
3. How should I cite the NIDS data?
Users wishing to cite the data should use the following reference for Wave 1, Wave 2, Wave 3 and Wave 4, respectively:
Wave 4 Data: Southern Africa Labour and Development Research Unit. National Income Dynamics Study 2014 - 2015, Wave 4 [dataset]. Version 1.1. Cape Town: Southern Africa Labour and Development Research Unit [producer], 2016. Cape Town: DataFirst [distributor], 2016. Pretoria: Department of Planning Monitoring and Evaluation [commissioner], 2014
Wave 3 Data: Southern Africa Labour and Development Research Unit. National Income Dynamics Study 2012, Wave 3 [dataset]. Version 2.1. Cape Town: Southern Africa Labour and Development Research Unit [producer], 2016. Cape Town: DataFirst [distributor], 2016
Wave 2 Data: Southern Africa Labour and Development Research Unit. National Income Dynamics Study 2010-2011, Wave 2 [dataset]. Version 3.1. Cape Town: Southern Africa Labour and Development Research Unit [producer], 2016. Cape Town: DataFirst [distributor], 2016
Wave 1 Data: Southern Africa Labour and Development Research Unit. National Income Dynamics Study 2008, Wave 1 [dataset]. Version 6.1. Cape Town: Southern Africa Labour and Development Research Unit [producer], 2016. Cape Town: DataFirst [distributor], 2016
4. What is a panel and/or longitudinal study?
Panel or longitudinal data consists of a time series for each cross-sectional unit (individuals, households, firms, countries, etc.) in the dataset, with the same cross-sectional units being followed over a given period of time. NIDS is a panel of roughly 30 000 individuals with four waves (or time series).
5. How frequent are the interviews?
NIDS goes to field every two years, with each repetition of the survey constituting a "wave".
6. How often is data released?
Data is released roughly every two years, following fieldwork.
7. What datasets are available?
Public release data is available for each wave. The data files that make up the NIDS dataset (within each wave) include:
- A link file (from wave 2 onwards) which lists the individual identifiers and the household identifier for each wave in which the respondent is resident, along with other pertinent information.
- Files for the household questionnaire, household roster and adult, child and proxy questionnaires.
- The household and individual derived datasets, containing variables that were not asked directly of the respondent, but were calculated or imputed from other information.
Secure data for waves 1, 2, 3 and 4 are also available at the DataFirst secure facilities in the School of Economics, University of Cape Town. Apply to access the data
The datasets are only available in Stata.
8. How can I access the data for my analysis and how do I register to use the microdata?
The NIDS data can be downloaded from the DataFirst website: http://www.datafirst.uct.ac.za/dataportal/
The available items can be viewed by searching for "NIDS" in the catalogue.
The steps to follow to gain access to the data are:
Step 1: Register as a user on the DataFirst website. Once you have registered on the DataFirst website the registration details can be used to access datasets from the site.>
Step 2: Complete a short online Application for Access to a Public Use Dataset form
Step 3: Download the data. Selected coding and syntax files can also be downloaded at this stage.
9. Am I eligible to access the data and will it cost me anything?
Accessing the NIDS data is free of charge and requires users to only fill out the online application on the DataFirst website, as well as agreeing to the stipulated terms and conditions.
10. How can I start analysing the data?
Read the documentation for each Wave of NIDS data, available here
11. Do I have to submit my research paper to NIDS?
Yes, as per the terms and conditions in the application for access and use of the data, a digital copy of all reports and publications based on the requested data must be sent to DataFirst.
12. Do I need to update all of my program files (do files) whenever a new wave is released?
Variable names have the wave number in the pre-fix. Other than that, the variable names are consistent across waves if the questions used to collect the data are equivalent across waves. However, it is advisable to always familiarize yourself with the questionnaire differences between waves and to read the documentation to see if there are changes that would impact on your analysis.
New versions of previously released data are accompanied with detailed documentation. In very rare cases variable names might change but this will be clearly documented. Program files should run effortlessly on new versions of previously released waves.
13. Is NIDS comparable to other longitudinal datasets?
The comparability of any longitudinal dataset depends partly on the sample, the questionnaires and the mode of data collection. NIDS is most similar to other personal interview household longitudinal surveys, such as Panel Study of Income Dynamics (PSID), British Household Panel Survey (BHPS), the Household, Income and Labour Dynamics in Australia (HILDA) Survey, Mexico Family Life Survey (MxFLS) & Indonesian Family Life Survey (IFLS).
14. The datasets that are posted for each new wave are called Public Release. What does ‘public release’ mean?
The data that is made available to the public, thus ‘public release’ data, goes through a process called anonymisation (removing personal information that could be used to identify respondents) in order to protect the identity of the NIDS respondents. Names and contact details are thus kept separately from the public release dataset and certain variables that are collected in field are not released or are only released at an aggregated level (e.g. occupation and migration data).
15. Where can I obtain information about release dates for files?
Each wave of the NIDS data is released approximately every two years with both the DataFirst website (http://www.datafirst.uct.ac.za/home/) and NIDS website (http://www.nids.uct.ac.za/) being updated with announcements regarding exact release dates. Registered users also get notifications regarding other data release information (including notification for administrative data).
16. Why does NIDS provide weights for analysis?
Weights help to maintain the representativeness of the sample to the population of interest.
17. What is the difference between the 2001 geographical variables (Province, District Council and Geo-type) and the 2011 geographical variables in the hhderived data set?
The 2001 variables are based on the 2001 StatsSA Census boundaries and the 2011 variables are based in the 2011 StatsSA Census boundaries. Prior to the public release of Census 2011, NIDS had circulated these variables based in the 2001 StatsSA Census boundaries.
See document NIDS Wave 4 Panel User Manual that outlines important cautionary notes about the differences between 2001 and 2011 geography.
18. Were there changes to imputed variables as a result of the use of the 2011 geographical variables?
The values are calculated using the 2001 geography variables where applicable. The Program Library contains the syntax files used to calculate the household income and expenditure.