A riddle about the subject of Economics has been cited in print since at least 2003:
   
Q: What would Economics be without assumptions?
A: Accounting.
 
“Economics without assumptions is accounting” and “Accounting is economics without assumptions” have both been cited since at least 2007.
 
   
Google Books
The Firm of the Future:
A Guide for Accountants, Lawyers, and Other Professional Services
By Paul Dunn and Ronald J. Baker
Hoboken, NJ: John Wiley & Sons
2003
Pg. 231:
The accounting profession has simply not taken the lead in this area. The reason may be explained by a joke told by a graduate economics student: One day in microeconomics, the professor was writing up the typical “underlying assumptions” in preparation to explain a new model. I turned to my friend and asked, “What would Economics be without assumptions?” He thought for a moment, then replied, “Accounting.”
     
VeraSage Institute
Debits Don’t Equal Credits
April 6, 2006 by Ron Baker
(...)
The accounting profession proffers little help in achieving this objective for a very fundamental reason: Accounting is not a theory.
 
Developing leading indicators requires evolving a set of falsifiable theories the business can test to determine the relationship between those indicators and future financial performance. The accounting profession has simply not taken the lead in this area. The reason for this may be explained by a joke told by a graduate economics student:
 
One day in microeconomics, the professor was writing up the typical “underlying assumptions” in preparation to explain a new model. I turned to my friend and asked, “What would Economics be without assumptions?” He thought for a moment, then replied, “Accounting.”
 
Google Groups: alt.humor.jewish
Economics anyone?
Ray
3/27/07
(...)
Economics without assumptions is accounting
         
The lighter side of accountancy and tax
Wednesday, July 18, 2007
Accountancy quotes
(...)
Accounting is economics without assumptions.
 
Google Books
Sensible Nonsense.. Frank’s Comic Pack:
Humour Pack Series
By Frank Paul
BookBaby
2014
Pg. ?:
What would Economics be without assumptions?Accounting.
 
Twitter
Beverley Thomas‏
@Kokm007
Daily giggle: What would Economics be without assumptions? Accounting
4:00 AM - 11 Dec 2017
 
Twitter
Lucky Score‏
@LuckyScoreNet
What would Economics be without
assumptions?
Accounting
#Joke from #AccountantJokes in #Jokes, #Humor and #Satire
12:36 AM - 1 Jan 2018