GDP 15-20% higher? Well actually:
The United Kingdom's economy grew by 0.3 percent in 2023, after a growth rate of 4.8 percent in 2022. 8.6 percent in 2021, and a record 10.3 percent decline in 2020.
What people refer to is the impact that coming out has had. Be it reduced exports, additional paperwork or restructuring a business. Just to give you an example: Easyjet were based in the UK with all aircraft registered here. To allow them to continue to fly intra-EU flights unrestricted, they had to set up a completely new entity in an EU country(Austria), and re-register 140+ aircraft. Not only did this cost them in excess of £10m but it also sucked that out of the UK. Now. I know it's only a small amount in the whole scheme of things, but 1000s of organisations went through similar re-structuring and the associated costs, much of which was then passed onto...us!
I'm sorry but this is ridiculously ignorant. Did you forget what happened in 2020 when a virus destroyed our entire economy and sent us home for months on end? A time when we were paying people 80% of their salary to not work? A virus with a total cost to the economy of at least £300bn, a £5,000 cost to each individual person?
That was a real event that mattered greatly to the economy and it also affected the global economy. The EU affects trading nuances within the EU which ultimately don't matter that much, especially given 50% of our trade is with the rest of the world where those nuances are irrelevant. If it mattered so much and was so beneficial then why is Europe itself doing so badly? Reading on here I'd expect European countries to be posting 1,2,3,4% growth whereas we'd be stuck in the mud but it's totally untrue, they're literally doing no differently to us.
We can name minutiae losses in trade figures but these are perfectly explainable by major events such as COVID or the Ukraine War which is why the exact same losses are also occuring elsewhere in Europe. Nobody can still explain to me why Brexit was the apocalypse and yet the largest EU economy Germany is doing no better than we are. You can't say that the Ukraine war is causing German struggles and yet in the UK it's absolutely Brexit, it's nonsense.
I can't even be bothered to link it but just look at UK total GDP today. It is at the highest that it has ever been. We were told that there would be an apocalypse immediately post-Brexit, there hasn't been, I'm still waiting for it to happen. I looked at our GDP growth for the entire of the 2010's and it wasn't affected in the slightest by Brexit. The only major stressor and economic shock was in Q1 2020, again please just Google what happened in Q1 2020....
Your argument around passed on costs is also mute, we've just had an inflation boom that was not caused by Brexit, it aligned exactly to what the rest of Europe experienced and was directly caused by the Ukraine war. Following monetary intervention why is inflation now more or less exactly the same as Europe? Where is Brexit in this? Again it's just nonsensical.