Average starting salaries give a clear indication of what type of training society needs its new workers to have. Certainly, there are benefits to a college major beyond the job a student can perform. But if we're talking about the benefits to society - as opposed to the benefits to the student - the only thing that matters is what the major enables the student to produce for society. And the value of what the student can produce is reflected in the wage employers are willing to pay the student to produce it.