“The average person thinks he isn’t”

“The average man thinks he isn’t” is from the New York City humor magazine The Judge in 1927. “The average person thinks he isn’t” has been credited to Father Larry Lorenzoni, in the San Francisco Chronicle from the 1980s.
 
 
Google Books
January - June 1927, The Judge, pg. 266:
The average man thinks he isn’t.
 
19 May 1934, Salt Lake Tribune (Salt Lake City, UT), “The Senator From Sandpit,” pg. 4, col. 2:
The average man thinks he isn’t.
 
Google News Archive
19 February 1951, Miami (FL) Daily News, pg. 1, col. 2 ad:
The Average Man Thinks He Isn’t
In appraising himself, it’s been said, the average man doesn’t think he’s average at all!
(Want Ad advertisement—ed.)
 
5 December 1957, Salt Lake Tribune (Salt Lake City, UT), “Senator From Sandpit” by Ham Park, pg. 21, col. 3:
The average man thinks he isn’t.—Judge.
 
29 March 1987, Chicago (IL) Tribune, “Runners” by Cheryl Lavin, Sunday Magazine, pg. 6:
“The average person thinks he isn’t.” Larry Lorenzoni
 
Google Books
14,000 Quips & Quotes:
For Speakers, Writers, Editors, Preachers, and Teachers
By E. C. McKenzie
Grand Rapids, MI: Baker Book House
1990, ©1980
Pg. 246 and Pg. 319:
The average man thinks he isn’t.
 
Google Books
Statistics Alive!
By Wendy J. Steinberg
Thousand Oaks, CA: Sage Publications
2011
Pg. 270:
The average person thinks he isn’t. —Father Larry Lorenzoni, in the San Francisco Chronicle