[TheOtherHobbes]

It's correlation. The cause is rationed access to the cultural - never mind the economic - resources needed to get into a graduate program.

Success after the program is an effect - and partly down to luck, as the SA article suggests.

Of course you'll have problems if you don't have a high school diploma. But by the time you've failed to get your diploma, the chances are excellent that your access to resources will have been severely constrained and rationed for your entire life, even if you start off with exceptional talents.

[adventured]

It's cause. What you're referring to is the cause of education deprivation. That education deprivation is the cause of the far lower likelihood of reaching higher wealth status.

A chain of things or events can - typically does - possess multiple causes along the pathing. A cause of a cause, is a legitimate, normal and required logical concept. Practically any outcome or condition you can name has a cause, which has a cause.

Alternatively you'd have to claim that there can only be one cause in an entire chain of events. An absurd notion.

[abecedarius]

It can be causal and still be a wasteful signaling game. I think that to first order that's what's going on.