Examples of analysis methods
You will find in this sub-section an introduction to a few analysis methods that can be used by the NIPN:
A. How to calculate the Average Annual Reduction Rate (AARR)
B. Using the Lives Saved Tool (LiST) in the context of NIPN
Since the adoption at the World Health Assembly in 2012 of 6 nutrition targets for 2025 (WHO, 2012) and their integration in the Sustainable Development Goals, two questions are raising growing attention:
- What is the current trend of the six nutrition indicator?
- Is the current trend sufficient to reach the target?
The current trend is measured by the “current AARR” (Average Annual Reduction Rate). The “required AARR” provides an estimation of the AARR necessary to reach the target.*****
Definition of the AARR by the World Health OrganisationThe Annual Average Rate of Reduction (AARR) is the average relative percent decrease per year in prevalence or rate. Thus, a positive sign indicates reduction or downward trend, while a negative sign indicates increase, or upward trend.
Source: WHO, AARR definition and technical notes.
The AARR is mainly used for stunting but it can be used for other indicators as well.*****
The standard calculation method, based on an exponential function, is well described in the UNICEF note for estimating AARR (see additional information below).
The formula is relatively simple but the result will highly depend on the parameters that are used to generate the AARR.
- AARR is a reflection of the trend of prevalence. If you use the data from the past 5 years or the past 15 years, the trend will differ and the AARR will not be the same. When generating a AARR value, the period under consideration needs to be exactly defined.
- AARR will obviously depend on the surveys included in the model. International initiatives usually rely on all the surveys of the JME (Joint Monitoring Estimates) database. But the EU relies on the EU database which is slightly different. The JME database may be slightly different from the database of National Statistical Offices. A decision must be made on whether to include or exclude some surveys depending on the data quality criteria (refer to the guidance note on data quality, section 3.3).
To calculate the “required AARR to reach the target”, additional parameters must be included in the model:
- The required AARR will obviously depend on the target (WHA targets; national target; targets from the Multisectoral Plan of Action for Nutrition…). This needs to be specified.
- If the target is a ’Number of children’, the required AARR will depend on the estimated number of children at baseline and at the time of the target. Different demographic models can be used, each with different scenarios and each are updated regularly. The model used need also to be specified. International initiatives usually use the WPP model (see additional information below).
When generating the AARR and the “required AARR”, 4 parameters must be specified:
- The time period under consideration
- The nutrition surveys which are included in/excluded from the calculation
- The target
- The demographic model (in case the target is a number of children)
A simple Excel spreadsheet or statistical software can be used for the regression to calculate the AARR.*****
Important international initiatives are regularly publishing AARR figures at international and national levels for monitoring and policy purposes:
They all use the same model but for various reasons, they use different parameters to calculate the AARR (see additional information below). In particular, the time period considered differs (some using only quite recent data, some using longer time periods). In 2017, the WHO-UNICEF TEAM group developed a report to harmonise the calculation of the AARR.*****
Take away messages
- Most of the initiatives have adopted the 2017 TEAM recommendations.
- EU method differs from TEAM mainly for current AARR calculations that are based on historical data (TEAM recommends using only recent data) and on the choice of the baseline year, which is fixed at 2012.
- The WHO tracking tool allows users to set their own target: countries are encouraged to set their own targets to fit with the timing of national plans and to set realistic goals.
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