View source for Occupational licensing

Occupational licensing is the process of obtaining permission from a government to practice a profession or trade. According to S. David Young, "today at least a fifth, and perhaps as much as a third, of the work force is directly affected by licensing laws" in the United States. 
[http://www.econlib.org/library/Enc1/OccupationalLicensing.html Library of Economics and Liberty article on occupational licensing]

According to Morris Kleiner:
"Occupational licensing has either no impact or even a negative impact on the quality of services provided to customers by members of the regulated occupation. Additionally, as occupations become licensed, members of regulated occupations see their earnings go up."
[http://www.instituteforjustice.org/index.php?option=com_content&task=view&id=2057&Itemid=165 A Primer on Occupational Licensing from the Institute for Justice]