How is dramatically lowering since 1970s compatible with stable after 1955? The fact is tax on the rich started going down in the 1970s and since the 90s tax havens and other shenanigans like renting out your own mega yacht to off shore shell companies even though you were using it. And a million other ways these people don’t pay.

For the richest tax is optional to the point where that get loans against their shares rather than pay capital gains tax. It’s an absolute disgrace and it’s got to a point where governments need to taxing them properly.