New mortality assumptions method for national population projections

Closes 20 Feb 2023

Opened 9 Jan 2023


National population projections (NPPs) serve a wide range of users across government and beyond. The primary purpose of the NPPs is to provide information on potential future population levels of the UK and its constituent countries. We base NPPs on the latest mid-year population estimates, together with assumptions of future levels of fertility, mortality and migration. 

We have developed a new mortality projection methodology for the NPPs as part of our strategy to continuously review and improve our methods. This new mortality projection methodology offers improvements in efficiency, replicability, and greater transparency than the current method. ​ 

A formal decision on the mortality projection method to be used in the NPPs will be made following the results of this user engagement.​ If we decide to adopt the new method, then we plan to use it for future rounds of NPPs. These will include the 2021-based NPPs, which have a provisional publication date of December 2023.

The proposed new mortality projection method uses an age-period-cohort (APC) model that is a well-established approach for projecting mortality improvements. This model has been developed by the Office for National Statistics’s (ONS) Methods and Quality Directorate in collaboration with the University of Southampton and the University of Warwick. The method fits linear models to historical data (separately for males and females, for both the UK and Scotland). The fitted values from the model are then used to project mortality improvement rates into the future. 

Our supporting article, Prospective new method for setting mortality assumptions for national population projections, UK: January 2023 explains the new prospective mortality projection method in detail. It also highlights initial comparative results between the current method and the proposed model for 2018-based and 2020-based NPPs. 

We are seeking feedback on the impacts and implications from the prospective change in our mortality projection. We are particularly interested in hearing from users of ONS statistics who use the NPPs, either directly or indirectly (for example, past and projected period and cohort lifetables). 

We are committed to following the principles of the Code of Practice for Statistics, consulting with our stakeholders to hear as many views as possible. Your feedback will contribute to decision-making on the ONS mortality projection method for future rounds of NPPs. 

How to respond 

We welcome contributions from all users of population projections. This includes, but is not limited to: 

  • government and government agencies,
  • interest groups,
  • charities,
  • civil society organisations,
  • academia.    

Before responding we recommend reading: Prospective new method for setting mortality assumptions for national population projections, UK: January 2023

You can also respond by email or post, using the downloadable version of this questionnaire which can be found at the bottom of this page in "Related". 


If you prefer a different format, or you would like to have a meeting with us to provide your feedback, email

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