It’s a pro union propaganda piece. They’re claiming that not being able to join a union drove wages down.
Unions only work when the unions are allowed to use Mafia enforcement tactics to intimidate employers and nonunion workers. Unions are the opposite of a free market.
If you want immigrants and their low wages out of the equation step up enforcement against employers who fail to verify citizenship and don’t pay the required taxes on their employees. Unemployment insurance and the like are all taxes on hiring people. Hiring illegals is about more than wages as they are often paid the same. The driving functions are taxes and labor regulation. I was having a drink with the owner of a company when he got a call from one of the labor regulation offices. He rolled his eyes in disgust saying, “I hired an accountant and a firm to do payroll to try and cut down on the fines and even with a full time staff doing a great job they still find ways to ding me.” (Some Florida offices are “self funded” meaning they only make their payroll when they fine somebody. In order to do that they generate mountains of regulations, some of which are “criminal” and the violation of them require a prison sentence. Unless, you pay the fines. The government has become the Mafia but with major medical and dental plans.)