D. Ongoing review of underpinning assumptions
D. 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.
Actions taken and commitments made by ONS to meet the recommendation
ONS told us that when the model was in use, the team had monthly checkpoints with ONS methodologists to review the assumptions and their impact on the statistics.
ONS also seeks external challenge for many aspects of the statistics, including model assumptions through the Migration Statistics Expert Group as well as methods assurance panels including the methodological assurance review panel (MARP).
OSR’s evaluation of evidence
While the state space model was in use, we were satisfied that ONS reviewed the model assumptions at regular intervals with experts as part of this development process.