You're right, I simplified for the example and assumed only one canonical job for each major. However, that doesn't undermine my criticisms. You'd still have to multiply each job by the amount that the degree helps you get that job.
So it's probably pretty hard to become a quant without a degree, so multiply that by some high number like 95%, but it's really easy to become an entrepreneur without a degree, so multiply that by some low number like 20%.
You're also right about the relevant question being "what is a degree worth to me?" That makes prediction even harder because the value of the degree is largely going to depend on the person's opportunity cost of going to school. Consider Mark Zuckerberg, Facebook was the opportunity cost of his getting a degree, which would make the degree's "value" be several billion dollars negative.
So it's probably pretty hard to become a quant without a degree, so multiply that by some high number like 95%, but it's really easy to become an entrepreneur without a degree, so multiply that by some low number like 20%.
You're also right about the relevant question being "what is a degree worth to me?" That makes prediction even harder because the value of the degree is largely going to depend on the person's opportunity cost of going to school. Consider Mark Zuckerberg, Facebook was the opportunity cost of his getting a degree, which would make the degree's "value" be several billion dollars negative.