Joe "The Plumber" Wurzelbacher, the Republican Party's newest working-class hero from Ohio, has been ridiculed and had his private life probed since he had the nerve to confront Barack Obama about taxation last week.

For liberals, one of Joe's biggest crimes against humanity - besides apparently owing about $2,000 in back taxes - is the charge that he works as a plumber but doesn't have a plumber's license.

In Ohio Joe's not required by law to get a license before he can practice plumbing. But he need to get a license if he decides he'd rather make his living as an accountant, architect, barber, chiropractor, cosmetologist, dental hygienist, dentist, paramedic, funeral director, hearing aid fitter, insurance agent, land surveyor, lawyer, nursing home administrator, nurse, occupational therapist, optometrist, pesticide applicator, pharmacist, physical therapist, physician assistant, physician, podiatrist, psychologist, public school teacher, real estate agent, real estate appraiser, school counselor, stock broker, social worker, truck driver, veterinarian or vet's assistant.

Before Joe Wurzelbacher or anyone else wants to become Joe the Barber or Joe the Podiatrist he must first get the permission of his state government.

In fact, every occupation above is licensed in all 50 states. That means before you go to work in those fields you have to pay whatever fees, pass whatever tests and meet whatever training, education or apprenticeship requirements your home state's professional and occupational licensing boards and commissions demand -- no matter how arbitrary, absurd or onerous they are.

Unfortunately, these 33 categories don't begin to show how widespread job regulation is. According to a 2007 study by the Reason Foundation, more than 1,000 occupations are regulated to some degree by states and about 20 percent of the country's work force must obtain a license to work (up from 4.5 percent in the 1950s).

The average state licenses 92 job categories, according to study author Adam Summers. California leads with 177 -- including talent agents and librarians. Missouri has the least -- 41 -- while Pennsylvania is remarkably low with 62. Among the most idiotic examples are Maryland (fortune tellers), Louisiana (florists) and Arizona (rainmakers).

Propagandists for these regulated occupations and their captive regulators in state government both insist, as Pennsylvania does, that job licenses are necessary to protect "the health, safety and welfare of the public from fraudulent and unethical practitioners."

Studies don't prove that, Summers says. And most economists -- including Milton Friedman, who shockingly but persuasively argued that "licensure should be eliminated as a requirement for the practice of medicine" -- see the scam behind the Nanny State smoke.

They know that occupational licensing is almost always a result of political lobbying by the very profession being licensed. And it is a sneaky way to use government power to protect the economic interests of incumbent doctors, lawyers and pesticide applicators.

By making it harder and more expensive for new doctors, lawyers and pesticide applicators to enter the market, competition and the number of practitioners in each field are artificially - and unfairly -- held down and salaries, prices and profits are propped up.

Consumers get robbed every day by this venerable public-private racket. So do those who'd like to become dietitians or auctioneers but can't afford the time or money for training or certification requirements. So does society, which gets less economic growth and innovation.

It's maddening. Because of occupational licensing, today Abe Lincoln couldn't practice law, Florence Nightingale couldn't be a nurse and Albert Einstein couldn't teach physics in a public school in America.

But don't despair. Our freedom to work isn't totally lost. Except for in Iowa, where you do need a license, any American can still grow up and become a manure applicator without getting the government's permission.