The Wealth of Nations by Part 1 Chapter 10 Page 93

An exclusive corporation necessarily weakens the force of this discipline. A particular set of workmen must then be employed, let them behave well or ill. It is upon this account that in many large incorporated towns no tolerable workmen are to be found, even in some of the most necessary trades. If you would have your work tolerably executed, it must be done in the suburbs, where the workmen, having no exclusive privilege, have nothing but their character to depend upon, and you must then smuggle it into the town as well as you can.

It is in this manner that the policy of Europe, by restraining the competition in some employments to a smaller number than would otherwise be disposed to enter into them, occasions a very important inequality in the whole of the advantages and disadvantages of the different employments of labour and stock.