“A movement is over when the news is out” (Wall Street adage)

“A movement is over when the news is out” is an old Wall Street adage, cited in print since at least 1906. The price of an asset reflects current value, but it also reflects what is believed to be its value in the immediate future (such as when quarterly earnings are officially announced). By the time the official news (such as a quarterly earnings report) is out, the stock price has already moved in reaction to the news. It is then too late to buy or sell on the news because the stock price has already gone up or down.
     
 
29 June 1906, Wall Street Journal, “The Wall Street Barometer”:
It is the constant phrase of the street that a movement is over “when the news is out.”
     
Google Books
The Technique of Short Selling;
Making money on declines in the stock market
Author: Mark Weaver
Palisades Park, NJ: Investors’ Library
1963
Pg. 53:
“When the news is out, it is unimportant.” This old Wall Street axiom is based on a long period of observations that the tape and the market generally ...
 
Google Books
A Treasury of Wall Street Wisdom
By Harry D. Schultz and Samson Coslow
Palisades Park, NJ: Investors’ Press
1966
Pg. 52:
It is the constant phrase of the street that a movement is over “when the news is out.” Stockholders and intelligent speculators operate not on what everybody knows, but on what they alone know or intelligently anticipate.
 
Pulist.net
The Evolution of Technical Analysis:
Financial prediction from Babylonian tablets to Bloomberg terminals
By Andrew W. Lo and Jasmina Hasanhodzic
Hoboken, NJ: John Wiley & Sons
2010
From the Inside Flap:
“A movement is over when the news is out,” so goes the Wall Street maxim.