I don't have to make up statistics to tell you that 100% of the economy is what's called a complex-adaptive system.
Experimental economics has shown time after time after time that no matter how perfect the information, no matter "expert" the participants, bubbles and the business cycle are merely facts of life, and attempts to centrally control or influence decisions leads to greater swings. The same question, asked later in time, is based upon different information than the original one. The only way to find out who's right is to wait and see what happens, there are theoretical frameworks to use as general ideas of how participants should act in such markets, the most compelling to me being the logarithmic regressions done by Thomas Dalton showing that the more a central entity exerts force over market participants, the more uncertainty these participants ultimately face.
As for being held accountable for something, I ask, for what? For voicing their opinions? People could've been right, with completely illogical thought processes, and they should be praised? It's not like economic analysis is a law with rigid consequences, it's the study of markets, which again, are one of the most complex institutions in modern day society. They offer great advantages, but the fact that [insert made up percentage] of them were wrong, what do you want to hold them accountable for? Should we fine them? They didn't make you do anything. In the sense of macroeconomics, predicting "right" and "wrong" are almost futile, as it all depends on what happens, which depends on an infinite number of decisions made infinite times a day by everyone who is hoping to act in their own best interest given the structure they're presented with.
People are held accountable in that when they choose "wrong", they end up with diminished utility than they would experience if they were "right". Saying economist should be held accountable for having a wrong opinion, while the correct one is only verifiable after see what happens, is like asking me to guess what the windspeed will be outside my office in 2.5 months - I can look at forecasts, I can learn metrology, make all the "correct" assumptions, give you my answer, and you serve me a consequence for telling you something that not only should you not solely rely on my opinion for, but that is realistically impossible
to know with absolute certainty anyway.
Fend for yourself. Life's unfair, be lucky.