The real question is whether this earnings difference is justified (the college degree adds enough value to the employee to put them on an entirely separate tie

The real question is whether this earnings difference is justified (the college degree adds enough value to the employee to put them on an entirely separate tier) or a "bubble" (perceived by hiring managers to be that important, but not actually). If the latter, many companies are making expensive mistakes by not hiring less-educated but intelligent workers. The costs of training would be far lower than the salary savings . My sense is that most employers today have no interest in serious training and career advancement for their employees. They hire technicians, engineers, and managers, rather than hiring technicians and letting them work their way to being engineers and managers. As a result, individual workers have far less space to grow within the company, loyalty is lower, the management has no personal experience of the day-to-day operations of the company.