> The price is driven up by "demand" but the demand is not "real" because it wasn't due to the business actually _innovating_ but actually just "stock changing hands"?
The demand is real, but the fundamentals do not support it. Fundamentals include things like price vs. earnings or debt vs. assets, dividend yields, etc.
If you like at this graph of price vs. earnings, you can can see dramatic rises relating to stock market bubbles:
https://www.multpl.com/shiller-pe
> When/how does that happen?
It has already happened and we're in the middle of it. When the markets tanked in late 2018, the Fed stopped hiking. When the markets tanked again in May, the Fed announced a rate cut. Now that the rate cut is in place, the markets are tanking again, perhaps because a bigger rate cut was priced in. We'll see what happens in the coming months.
> There is no way for it to "not" right? It's sort of like measuring volume of action, but the action didn't actually produce any real "value"?
I guess that's a fair way of looking at it.
> Is there a better measure that _does_ reflect it?
Of course there are indicators that you can use to show that this kind of inflation is taking place, like the S&P 500 PE ratio I showed earlier, or rent income vs. property prices.