“Why in the world do we regulate barbers?” asked Mark Hutchison, a Republican and the lieutenant governor of Nevada, which shares billing with Arizona as one of the states with the most burdensome licensing requirements, according to the Institute for Justice. “A bad haircut is the last thing that a person is going to put up with and return to. It is the ultimate example of self-regulating industry.”

The problem is particularly acute for military spouses, who move frequently, as well as veterans and immigrants, who may have extensive training but lack a particular state’s seal of approval. And there are at least 27,000 different licensing restrictions across the states affecting people with arrest and conviction records. Most of them permanently disqualify applicants, meaning a minor transgression as a teenager can prevent someone from working in many fields decades later.

The most regulated states, paradoxically, are red. “Even Republican governors with Republican legislatures in pretty conservative states have still found it extremely difficult to effect change,” said Dick M. Carpenter, strategic director of the Institute for Justice. “When there is an effort to dial back legislation, then the licensed industry turns out with huge counterattack. This is the same story that plays out in every state.”

Only rarely are licensing requirements removed. Last month, though, Arizona agreed to curb them for yoga teachers, geologists, citrus fruit packers and cremationists.

But dozens more professions escaped the ax. “Arizona is perceived as a low-regulatory state, but this was the most difficult bill we worked on this session,” said Daniel Scarpinato, a spokesman for the Republican governor, Douglas Ducey.

Licensing boards are generally dominated by members of the regulated profession. And in Arizona, more than two dozen of the boards are allowed to keep 90 percent of their fees, turning over a mere 10 percent of the revenue to the state.