What’s more, it is demonstrably not the case that income levels simply reflect aptitude and effort. Now, obviously being from a richer family affords all sorts of advantages, including physical, emotional, and cultural development. But factor all that out of the equation and assume that it’s just fair for all those things to translate into higher academic performance and higher earnings.
Even assuming that, there are massive advantages inherent simply in being born rich (and disadvantages in being poor.) My favorite example, simply because it’s so dramatic, is that a child born into the lowest-earning quintile who manages to attain a college degree is less likely to be in the highest-earning quintile than a child born into the top quintile who does not attain a college degree. This is all the more remarkable when you consider that making it to, and through, college is far harder for poor kids than rich kids even at a given level of aptitude. (Two thirds of the kids with average math scores and low-income parents do not attend college, while almost two-thirds of high-income kids with average math scores do.)