I think you are, perhaps, playing with the definition of causation in a strange way. Causation is constant conjunction of events; that these things are correla

I think you are, perhaps, playing with the definition of causation in a strange way. Causation is constant conjunction of events; that these things are correlative, and that there are other mitigating factors possibly leading to both at the same time, does not mean that there is not a causal relationship between them. Correlation does not imply causation, but it also doesn't prohibit causation. None of the things that you listed really have an effect on a causative relationship between education and income (even though they might be contributing factors to both). From a common sense perspective, quite a number of high paying jobs require a technical or professional degree. When you post a job listing, there are often educational requirements. If you don't have a college degree, the highest paying fields, such as doctor, lawyer, engineer... are completely closed off to you. With the industrialization of HR in modern companies, certain things, like years of education, are certainly used to 'weed out' candidates. (Try applying to an engineering job with just a GED). Aside from that, the author isn't really implying a causal relation, he is just stating a strong statistical correlation. If you want to make a boatload of cash, chances are that getting an education is a good idea.