Source of quote about businessmen conspiring when they meet

Question

I'm trying to find the source of a quotation, which goes something like, "when two businessmen meet, they will naturally conspire to create a consortium against the interests of a third". This is an approximation; I think the quotation might also say something about conspiring against the common good.

I believe it may have been written by an American, maybe Mencken, although he wrote so much it is probably just natural to suspect him.

Answer 1

This is from The Wealth of Nations (1776) by Adam Smith:

People of the same trade seldom meet together, even for merriment and diversion, but the conversation ends in a conspiracy against the public, or in some contrivance to raise prices. It is impossible, indeed, to prevent such meetings, by any law which either could be executed, or would be consistent with liberty and justice. But though the law cannot hinder people of the same trade from sometimes assembling together, it ought to do nothing to facilitate such assemblies, much less to render them necessary.

_{Adam Smith (1776). An Inquiry into the Nature and Causes of the Wealth of Nations, book I, chapter X. Project Gutenberg.}