Stock-market legend who predicted 3 financial bubbles says this is Real McCoy

> The great bubbles can go on a long time

What he said may be true, but that doesn't mean it's useful. By this logic, you can just say that stocks are overvalued any time after they've recovered from a prior bubble pop or they go over a certain P/E ration, and you'll eventually be right given a long enough timeframe for a correction, but you might miss out on decades of growth in between.

I think a big problem is everyone is in, “Central banks are on the case and will save us” mode. It’s still an unprecedented route to take. There’s a lofty exuberance to the Hertz rally, in particular, that seems completely detached from the current reality.

What's the false positive rate, false negative rate? Does he also correctly predict when there will not be a bubble?

His fund family actually publishes equity index forecasts in its research library [1].

That means you can evaluate the efficacy of his research team's forecasts over time.

I happen to think he is correct, but process matters. How has the process held up over time?

[1] https://www.gmo.com/