My summary of Gary's basic argument
I originally posted this on another subreddit where they were doing character attacks on Gary, but I feel like this summary may help the people in here as well. Feel free to correct me if I made any mistakes.
Here's the plot you should actually care about (yes this is US, not UK but it's what I'm able to find, and Gary's arguments apply to the US too): https://fred.stlouisfed.org/series/WFRBLTP1246 US inflation since 1990 is ~155% so you divide the right edge of the graph by 2.5 but it still shows the growth. Yeah sure maybe they were richer in the gilded age, but I don't think we want to go back to that.
Why do we care about the 0.1%, not the 1%? Well that's who Gary usually targets with his proposed wealth taxes. I believe it can be mathematically shown that untaxed or low-taxed wealth leads to wealth accumulation, because wealth always compounds faster than the economy grows. Sure, you can say some eye-watering numbers like "Bezos paid 1.4 billion dollars in taxes between 2006 and 2018". But when you realize it's less than 1% of his net worth over 12 years, you can see it's doing nothing to stop his wealth accumulation.
Gary's argument is that asset prices then all go up because the ultra-rich have nothing to spend their wealth on other than assets (you can only buy so many private jets, yatchs, supercars...), so their accumulating wealth, which IS provably becoming a larger and larger fraction of all wealth: https://fred.stlouisfed.org/series/WFRBSTP1300, is used to buy assets, faster than the growth of the economy can create new assets.