George, I think you should probably begin with the history of the  
professional societies (like HES). As an example, you might try  a  
couple of papers by A. W. Coats: 
 
Coats, A.W.(1964) "The American Economic Association." American Economic  
Review. 54 (4): 281-5. 
 
Coats, A. W. (1991) "Economics as a Profession." chapter 8 in Greenaway,  
David, M. F. Bleaney III, and Ian Stewart (ed.). Companion to  
Contemporary Economic Thought. London: Routledge. 
 
Some list members are better in touch with the literature than I. So  
these references are only an entrance point. 
 
My approach to the subject would be less broad than Larry's. I would  
begin with the recognition that professional ethics cannot begin until a  
distinct group of people begin to think of themselves as part of a  
(i.e., of the same) profession. Professional ethics from this point of  
view is not a kind of ethics in the philosophical sense. It is rather a  
set of principles that a distinct group agrees, in one form or another,  
to express a wish to follow.  It is more like a sociological bond. 
 
Professional ethics of this type probably began first in England or  
Europe with the first economics societies. But I would guess that the  
AEA is an interesting case to study because the people who formed that  
society were most likely less elitist. So some of them probably  
developed a conception of ethics that was more considerate of the  
"common man." 
 
Mises writes about economics as a profession, yes. But he does not write  
about the ethics of the profession. He saw the group that calls itself a  
profession mainly as a political pressure group (thinking of Europe, I  
suspect). 
 
On the more substantive issue, shouldn't the primary ethic of economists  
be to define their subject matter and, having done this, to set up  
institutions that would enable contributions to the study of that  
subject matter to be gleaned from the non-contributions? 
 
Pat Gunning