TLDR Not so simple.

First, purchasing power is not considered. If wages are stagnant, but most consumer goods have gotten cheaper, then the bottom 50% with stagnant wages is capturing productivity gains.

Second, there’s no account for economic mobility. Wages for the bottom 50% are stagnant but most people don’t stay the same income all their life. There’s no account of economic mobility.

From the article: “As in the other panel studies, when you follow the same people, the biggest gains go to the poorest people. “