How about a few more of them: Union contracts, prevailing-wage laws, and the Jones Act.
And, the most important external intervention of all...
Massive legal and illegal immigration.
In 2013, we issued 1.1 million new Green Cards, most of them to low skill, low education workers.
In 2013, we created 750,000 new citizens, most of them low skill, low education workers.
In 2013, we issued or extended about 650,000 work visas, most of them to medium skill workers.
In 2013, we had about 7 million illegal workers, most of them low skill and low education.
The “natural” wage scale for low skill workers in America has been crushed.
The “natural” salary scale for certain skilled occupations in America - like software engineers - has been stagnant for 15 years.