“It’s not what you know, but who you know”

“It’s not what you know, but who you know” is a saying used in both business and government. The origin of the saying is unclear, but there are two labor citations of the phrase in 1914 and 1918.
 
“It’s not what you know, it’s who you know” became frequently used after 1937.
 
“It’s not who you know, it’s whom you know” is a jocular take on the saying.
   
     
Google Books
May 1914, The Electrical Worker, pg. 233, col. 1:
Many devious forces apparently also control the conditions of advancement and preference, and a phrase that is often heard is to the effect that it’s not what you know that counts so much, as who you know!
 
Chronicling America
22 September 1918, New York (NY) Tribune, “U. S. to Act to Oust Ship Work Slackers,” pg. 9, col. 1:
PHILADELPHIA, Sept. 21.—The shipyard workers along the Delaware River have adopted a war slogan all of their own. It is: “It’s not what you know; it’s who you know.”
     
Google Books
Printer’s Ink
Volume 179
1937
Pg. 11 ad:
HELP WANTED
June Grads. Male—Female. Want to enter “advertising-printing game”? Use us as stepping-stone. “It’s not what you know but who you know.” Write Irving Rosen Associates, 1133 Broadway, N. Y. C.
   
16 July 1938, Chicago (IL) Daily Tribune, “Looking at Hollywood” by Ed Sullivan, pg. 9:
Anita M. Chambers, Washington, D. C., agrees with George Shapiro that today “it’s who you know, not what you know.”
     
5 August 1938, Los Angeles (CA) Times, “Bill Henry Says,” pg. A11:
Better tip ‘em off to this Vine and Hollywood Boulevard gag—“It’s not what you know, it’s who you know!”
 
Google Books
Liberty, employment, and no more wars
By Theodore Kinget Quinn
New York, NY: Hastings House
1943
Pg. 33:
“It’s not what you know but who you know that matters,” was quoted as a gem of wisdom.
   
Google Books
29 September 1947, Life magazine, pg. 128, col. 2:
“There’s a saying in business today,” a ruddy young man with a cheerful competent manner takes up the story. He was a squadron commander in the RAF and is now manager of a plant that manufactures leather goods. “It’s not what you know, it’s who you know…It helps if your suppliers have had long dealings with your firm.”
 
Google Books
4 October 1948, Life magazine, “John Foster Dulles and his foreign policy” by James B. Reston, pg. 131, col. 1:
In Washington it is sometimes said that, in the selection of a Secretary of State, it is not what you know but who you know that counts.
   
OCLC WorldCat record
It’s not what you know (it’s who you know)
Author: Carl Jackson; Jerry Salley
Publisher: Santa Monica : Jack and Bill Music Co., ©1988.
Edition/Format: Musical score : English
   
OCLC WorldCat record
Networking for everyone: it’s not what you know, it’s who you know.
Author: Michelle Tullier
Publisher: JIST Works 1997.
Edition/Format: Book : English