Summary of recommendations
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- ONS should publish details of which data sources it intends to use for the ABME (strategic) and provisional state space model (tactical) approaches. It should also set out how each additional source impacts the migration estimates and the implications for how users should interpret the different provisional and final estimates.
- ONS should ensure data sources used in the estimates remain up to date. It should be clear with users how it will achieve this, for example by identifying points when it will review the data sources, such as use of historical IPS data and Home Office visa data.
- ONS should make the modelling approach more transparent and easier to understand for less expert users. It should support users to understand when and how to use the estimates calculated in this model, for example by writing an explainer piece on the state space modelling, including its strengths and limitations, and the impacts of different assumptions.
- ONS should keep under review the underpinning assumptions of the state space model and the impact of these assumptions on the use of these statistics.
- Users need a clear understanding of uncertainty associated with the estimates and how the estimates can be used appropriately. ONS should share detailed plans for how uncertainty will be measured and communicated.
- ONS should provide clearer information about its longer-term plan for measuring migration estimates. For example, what the longer-term model will look like and how the state space model method (tactical approach) and the admin-based method (strategic approach) will be integrated with this longer-term model and how this fits with ONS plans for a Dynamic Population Model.
- To help users understand the implications for their use of data, ONS should provide more detail on its plans to maintain a consistent time series, including the rational for its plans.
- To give users greater confidence in ONS’s quality assurance, ONS should set out its approach to validating migration estimates, particularly migration flows.
- ONS should improve the accessibility of migration data and information:
- relating to the migration transformation programme so it is clear to all users what is the most up-to-date data and information and what should be used in what context.
- available across Government so it is clear to users what related information is produced by other Government Department.
- To ensure all users, including non-expert users, understand its developing thinking ONS should publish and keep up to date a glossary of terms for the population, migration and labour market transformation programme (which is easy to navigate to) and ensure consistency in how it refers to emerging parts of the programme in its communications.
- ONS should publish a high-level roadmap for the population, migration and labour market transformation programme, including how migration fits with the rest of the transformation plans, when migration outputs are due to be published and how users can get involved.
- ONS should engage with a wide range of users to ensure the estimates available will meet the needs of a variety of users. It should also be clear on what the statistics can and cannot be used for and any decisions it has had to make based on the availability, strengths and limitations of the underpinning data which impact on use.
- ONS is planning further work to develop its thinking on how frequently migration estimates are updated. As part of this work ONS should engage with a wide range of users to ensure it:
- Understands how frequently different sets of users need updated migration estimates and why
- Understands user views on having provisional and final estimates
- Clearly communicates the difference between the provisional and final estimates, e.g. different data sources and/or methods used, and how this will impact different uses?