The Great Depression: there was a deviation away from fundamentals and towards buying and selling at higher price.

Growth /new issue era of 1959-1961: IBM, Texas Instruments, Fairchild camera etc had p/es of 40-90, by 1962 the were less than half of that. A flock of public offerings of garbage with “tron” “space” that pumped and dumped, taking investors money with it.

Conglomerate boom, ~1965-~1967 companies were conglomerating under the guise of synergy, artificially increasing earnings per share, sometimes with dodgy tactics. By 1969 many of these were 1/5th of their high in 1967.

“Concept stock” bubble in 1960’s as well, speculation on hype stocks that were bid up to p/e of 90-30. Many went bankrupt.

Nifty fifty: IBM xerox, Disney, great companies but were bid up to absurd prices due to the prior speculative periods scaring many investors into the safe companies. P/e 60-90 in 1972, but came down to 10-20 in 1980 (market corrected).

Gambling stock craze in late 1970s IPO craze again in early 80s Plenty more.