Source: The Human Side of Enterprise (1960), p. 11 (2006; 13)
“I am profoundly skeptical about our abilities to predict the future in general, and human behavior in particular.”
Source: The Anti-Post-Modern Post-Modernist http://errolmorris.com/content/lecture/theantipost.html
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Errol Morris 14
American filmmaker and writer 1948Related quotes

Source: Inventing the Future (1963), p. 161
George Katona (1951). Psychological Analysis of Economic Behavior. McGraw-Hill, New York. p. 31

“The tendency to be rational is the consistent and hence predictable element in human behavior.”
Source: Price Theory: An Intermediate Text, 1986, p.4

Source: 1930s, Principles of topological psychology, 1936, p. 11.

“It's tough to make predictions, especially about the future”
The earliest citations of this proverb, from the mid-twentieth century, refer to it as Danish in origin. See http://quoteinvestigator.com/2013/10/20/no-predict/
Disputed, Misattributed

“Prediction is very difficult, especially about the future.”
As quoted in Teaching and Learning Elementary Social Studies (1970) by Arthur K. Ellis, p. 431
The above quote is also attributed to various humourists and the Danish poet Piet Hein: "det er svært at spå – især om fremtiden"
It is also attributed to Danish cartoonist Storm P (Robert Storm Petersen).
Disputed
Variant: It's hard to make predictions, especially about the future.
"The Real Science Behind Changing Climate", LewRockwell.com, August 1, 2014. https://www.lewrockwell.com/2014/08/lk-samuels/the-real-science-is-suppressed/