● The analysis you link to is exactly the same sort of analysis the OBR provides -- i.e. a synthesis of current and past data and updated projections of what that means looking ahead
● The OBR report links to detailed "Economic and fiscal outlook" (EFO) data that includes the actual data the conclusions are based on. I haven't tried to look at the linked data for many of the analyses in the OBR report, but for those I have I find data in the cited EFO documents that seems to backup the statements made. For example, Box 2.6 of the March 2022 EFO report: https://obr.uk/box/the-latest-evidence-on-the-impact-of-brex...
● I gather that the "Institute of Economic Affairs" (IEA) is a long running right wing think-tank/advocacy group -- https://en.wikipedia.org/wiki/Institute_of_Economic_Affairs
● The director of the IEA was apparently recorded by an undercover reporter telling funders that his organization was in "the Brexit influencing game" [1]. Why should I thus trust that the IEA isn't trying to spin Brexit outcomes to their funders advantage? This applies to the government too of course, but many of those OBR/EFO reports seem to have been prepared when the Conservatives were in power.
[1] https://www.theguardian.com/politics/2018/jul/29/rightwing-t...