C. Transparency of the modelling approach
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.
Actions taken and commitments made by ONS to meet the recommendation
ONS used the state space modelling approach as a temporary methodology while researching and implementing administrative data sources. ONS is no longer using the state space modelling methodology in LTIM estimates. ONS had previously published Using statistical modelling to estimate UK international migration in April 2021 containing high level information and linked users to a more technical methodology paper providing users with some information, but an explainer piece has not yet been published.
OSR’s evaluation of evidence
We recognise that the complex nature of this method means that explaining it to non-technical users in a meaningful way is particularly challenging.
The published material provides users with either very technical or very high-level information but lacks mid-technical level information. It is important that ONS continues to recognise the different levels of technical expertise amongst its users and meets the needs of all user groups to maximise users understanding of the estimates and generate maximum engagement. Given that ONS are no longer using the modelling approach that this recommendation refers to, publishing additional material is no longer relevant.