Occupational Licensing Does More Harm Than Good

License, certification, accredition, etc., etc.: Yes.
Job quality / Performance measure: Not sure... Here is a book and a comment:

"It is well known that doctors, dentists, and lawyers must be licensed to practice their professions. But what about occupational therapists, manicurists and barbers? How about fortune tellers, massage therapists, shampoo assistants, librarians, beekeepers, electrologists and movie projector operators? These are just a sampling of the hundreds of occupations that require a license in at least some states or counties.

In a new book, "Licensing Occupations: Ensuring Quality or Restricting Competition?" (Upjohn Institute, 2006), Morris M. Kleiner, an economist at the University of Minnesota, questions whether occupational licensing has gone too far. He provides much evidence that the balance of occupational licensing has shifted away from protecting consumers and toward limiting the supply of workers in various professions. A result is that services provided by licensed workers are more expensive than necessary and that quality is not noticeably affected." ... continue reading

See also:

ALAN B. KREUGER. "Economic Scene; Do You Need a License to Earn a Living? You Might Be Surprised at the Answer." The New York Times (Thurs., March 2, 2006): C3.