This analysis is an opinion without proper analysis. There could be many other structural reasons. For instance, my gut says that the poverty is increasing even though the growth is good because the balance of trade for the USA has worsened significantly ever since the global trade took off [1] right around 1975, just at the beginning of the "decline" that this article talks about. So if someone in China is willing to do your job for $2/day, your wages are going to go down even as the investors benefit from increases in profits of the businesses manufacturing more in China. I wish the author had done at least a tiny bit of analysis, rather than spouting opinions based on inanities like "the tide lifts all boats". In this case, the boats of the poor are slowly sinking to the level of global wages for any given job.

[1] http://www.tradingeconomics.com/charts/united-states-balance...