The thing that really needs to be measured here is the real rate of return on these individuals' capital (i.e. post-tax returns) vs economic growth (i.e. growth

The thing that really needs to be measured here is the real rate of return on these individuals' capital (i.e. post-tax returns) vs economic growth (i.e. growth in wages for ordinary people). The point isn't really about when taxation occurs (I agree this is lazy in the article), it's more that once you factor in taxes (and most serious economists of inequality do this), you end up with more money via returns on wealth than via earning an income. So there's these two concepts, and they are sort of related because they show how the tax regime favors the wealthiest of the wealthy. But the article does a poor job of this.