“If all economists were laid end to end, they’d never reach a conclusion”

“If economists were laid end to end, they would not reach a conclusion” is a quip usually attributed to George Bernard Shaw (1856-1950), but there is no evidence that he said it.
 
In May 1933, “New York Day by Day” syndicated columnist O. O. McIntyre wrote: “The best answer to economics is Isaac Marcosson’s: ‘If all the economists in the world were placed end to end, they would not reach a conclusion.’”
 
Isaac Frederick Marcosson was the financial editor of The Saturday Evening Post and frequently wrote about economic issues.
 
     
Wikiquote: Economics
Unsourced
If economists were laid end to end, they would not reach a conclusion.
George Bernard Shaw
     
Wikipedia: Isaac Frederick Marcosson
Isaac Frederick Marcosson (1877-1961) was an American editor, born at Louisville, Kentucky, and educated in the schools of Louisville.
 
In 1903, he became associate editor of The World’s Work, and in 1907, he became a member of and financial editor of The Saturday Evening Post. From 1910 to 1913, he was editor of Munsey’s Magazine.
 
Google News Archive
20 May 1933, San Jose (CA) Evening News “New York Day by Day” by O. O. McIntyre, pg. 10, col. 6:
The best answer to economics is Isaac Marcosson’s: “If all the economists in the world were placed end to end, they would not reach a conclusion.”
   
Google News Archive
28 September 1933, Cape Girardeau (MO) Southeast Missourian, ‘Washington Letter” by Rodney Dutcher, pg. 4, col. 8:
Even statisticians can kid themselves. Some of them match the one about “if all the economists were laid end to end they’d never reach a conclusion” with the assertion that “if all the statisticians were laid end to end it wouldn’t make a difference.”
   
Google Books
Reader’s Digest
Volume 24
1933
Pg. 107:
If all the economists in the world were laid end to end, they would never reach a conclusion.
   
Google Books
Derby Day and other adventures
By A. Edward Newton
Boston, MA: Little, Brown, and Company
1934
Pg. 235:
It has been said that if all the economists were laid end to end they would reach around the world, but not a conclusion.
     
Time magazine
Business & Finance: Ithaca Sweatshop
Monday, Jul. 29, 1935
(...)
After presiding at one session of the conference President Harper Sibley of the U. S. Chamber of Commerce politely surmised: “If all economists were laid end to end, they would reach no conclusion.”
 
Google Books
Speaker’s Handbook of Epigrams and Witticisms
By Herbert V. Prochnow
Blackpool: A. Thomas & Co.
1955
Pg. 87:
If all economists were laid end to end, they would not reach a conclusion. George Bernard Shaw
 
15 March 1961, New York (NY) Times, pg. 39:
ISAAC MARCOSSON,
JOURNALIST, DEAD
Interviewed Leading World
Figures—Was Top Writer
on Saturday Evening Post
Isaac F. Marcosson, writer on political and economic affairs, died last night at Doctors Hospital. he was 83 years old.
 
A man who had traveled the world and interviewed as many of its noted personages as any other present-day journalist, Mr. Marcosson was believed to have been one of the highest paid correspondents of his day.
(...)
During the thirty years beginning in 1907, Mr. Marcosson was a leading writer for The Saturday Evening Post.
(...)
Isaac Frederick Marcosson was born in Louisville, Ky.