The main objective of the NPS is to provide high-quality household-level data to the Tanzanian government and other stakeholders for monitoring poverty dynamics, tracking the progress of the Five Year Development Plan (FYDP) II poverty reduction strategy and its predecessor plans, and evaluating the impact of other major, national-level government policy initiatives. As an integrated survey covering a number of different socioeconomic factors, it compliments other more narrowly focused survey efforts, such as the Demographic and Health Survey (DHS) on health, the Integrated Labour Force Survey (ILFS) on labour markets, the Household Budget Survey (HBS) on expenditure, and the National Sample Census of Agriculture (NSCA). Secondly, as a panel household survey in which the same households are revisited over time, the NPS allows for the study of poverty and welfare transitions and the determinants of living standard changes.
Kind of data
Sample survey data [ssd]
Unit of analysis
The universe includes all households and individuals in Tanzania with the exception of those residing in military barracks or other institutions.
Producers and sponsors
National Bureau of Statistics
Ministry of Finance and Planning
World Bank Living Standard Measurement Study Team
Bill and Melinda Gates Foundation
NPS Technical Committee
The NPS sample was refreshed for NPS 2014/2015. Longitudinal surveys tend to suffer from bias introduced by households leaving the survey over time (i.e. attrition). Although the NPS maintains a highly successful recapture rate (roughly 96% retention at the household level), minimizing the escalation of this selection bias, a refresh of longitudinal cohorts is typically done to ensure proper representativeness of estimates while maintaining a sufficient primary sample to maintain cohesion within panel analysis. Additionally, the refreshing of a longitudinal sample realigns the sample with any changes in administrative boundaries, demographic shifts, or updated population information. In the case of Tanzania, a newly completed Population and Housing Census (PHC) in 2012 providing updated population figures, along with changed in administrative boundaries, emboldened an opportunity to realign the NPS sample. Similar to the sample in NPS 2008/2009, the sample design for the “Refresh Panel” allows analysis at four primary domains of inference, namely: Dar es Salaam, other urban areas on mainland Tanzania, rural mainland Tanzania, and Zanzibar. The sample design is a stratified two-stage design. The design consists of 51 design strata (identified in the data as ‘strataid’) corresponding to a rural/urban designation for each of the 26 regions; however, Dar es Salaam is pure urban and therefore constitutes only one stratum. The allocation across the design strata was informed by the last round of the NPS and seeks to balance multiple survey objectives and maximize precision given survey parameters. The intended sample design consisted of a new selection of 3,360 households corresponding to 420 EAs from the latest PHC in 2012. This new cohort in NPS 2014/2015 will be maintained and tracked in all future rounds between national censuses. A nationally representative sub-sample was selected to continue as part of an “Extended Panel”. This “Extended Panel” allowed general comparison of sample groups and monitoring indicator comparability.
In order to produce nationally representative statistics with the NPS data, it is necessary to apply weighting or expansion factors. The panel survey weights adjust for differences in the probability of selection into the NPS 2008/2009 sample for observations in various strata, 2008/2009 households splitting into multiple households in 2010/2011 and splitting even further in 2012/2013, and attrition between rounds of the survey. The first round of the NPS sample was a multi-stage clustered sample design. First stage sampling involved the selection of survey clusters with the probability of selection proportional to cluster size within a stratum. The sampling of these clusters was stratified along two dimensions: (i) eight administrative zones (seven on Mainland Tanzania plus Zanzibar as an eighth zone), and (ii) rural versus urban clusters within each administrative zone. The combination of these two dimensions yields 16 strata. In rural areas a cluster is defined as an entire village. In urban areas a cluster is defined as a census enumeration area. As a general rule, the probability of selection was higher for clusters within strata where existing data sources showed that the variance of key variables of interest for the NPS (e.g., household consumption and maize production) were likely to be very high – implying the need for more observations to produce reliable estimates. The expansion factors for the NPS-EP 2014/2015, variable “y4_panelweight”, have been integrated into Section A, “HH_SEC_A” of the household dataset. Additionally, unique identifiers for the first-stage sampling units, “clusterid”, and for the sampling strata, “strataid” can also be located in Section A of the household dataset. The methodology used to calculate the panel weights for the NPS 2012/2013 was developed as part of the LSMS-ISA work program. Details on the methodology can be found in the paper: Himelein, Kristen. 2013. “Weight Calculations for Panel Surveys with Subsampling and Split-off Tracking.” Statistics and Public Policy, vol (1), pp40-45.)
Dates of collection
Mode of data collection
Additional data cleaning was conducted as the final stage of the data processing. Further adjustment of the data post-entry was conducted under the principle of absolute certainty where adjustments must be evidence-based and correction values true beyond a reasonable doubt. As such, the resulting final data files may still contain some inconsistencies and outliers. Handling of these values is thus left entirely to the data user. Throughout the data processing system, versions of the data are archived at all key steps and all checking and cleaning syntax documented and archived.
The Primary Data Investigator undertakes that no attempt will be made to identify any individual person, family, business, enterprise or organization. If such a unique disclosure is made inadvertently, no use will be made of the identity of any person or establishment discovered and full details will be reported to the NBS. The identification will not be revealed to any other person not included in the Data Access Agreement.
The dataset has been anonymized and is available as a Public Use Dataset. It is accessible to all for statistical and research purposes only, under the following terms and conditions:
1. The data and other materials will not be redistributed or sold to other individuals, institutions, or organizations without the written agreement of the Nationa Bureau of Statistics, Tanzania.
2. The data will be used for statistical and scientific research purposes only. They will be used solely for reporting of aggregated information, and not for investigation of specific individuals or organizations.
3. No attempt will be made to re-identify respondents, and no use will be made of the identity of any person or establishment discovered inadvertently. Any such discovery would immediately be reported to the National Bureau of Statistics.
4. No attempt will be made to produce links among datasets provided by the NBS, or among data from the National Bureau of Statistics and other datasets that could identify individuals or organizations.
5. Any books, articles, conference papers, theses, dissertations, reports, or other publications that employ data obtained from the National Bureau of Statistics will cite the source of data in accordance with the Citation Requirement provided with each dataset.
6. An electronic copy of all reports and publications based on the requested data will be sent to the National Bureau of Statistics
The original collector of the data, the National Bureau of Statistics, and the relevant funding agencies bear no responsibility for use of the data or for interpretations or inferences based upon such uses.
National Bureau of Statistics (NBS) [Tanzania]. 2015. National Panel Survey (NPS) - Wave 4 - Extended Panel 2014 - 2015. Ref.TZA_2014_NPS-R4_v03_M_v01_A_EXT. Downloaded from [URL] on [Date]. Dar es Salaam, Tanzania: NBS. (www.nbs.go.tz)
Disclaimer and copyrights
Although the data have been produced and processed from sources believed to be reliable, no warranty expressed or implied is made regarding accuracy, adequacy, completeness, legality, reliability or usefulness of any information. This disclaimer applies to both isolated and aggregate uses of the information. This data is provided on an "AS IS" basis. Changes may be periodically added to the information herein; these changes may or may not be incorporated in any new version of the publication(s). It is recommended that the user pay careful attention to the contents of any metadata associated with a file. If the user finds any errors or omissions, we encourage the user to report them to the data producer(s).