[tropo]

There have been huge gains at nearly all income levels, but not all. The groups missing out has been the 1st-world non-rich. Graph of it here:

https://avc.com/2016/08/elephant-chart/

(note that the green line marks the mean gain, at about 25%, not zero)

So the typical 1st-world person sees people on both sides of them gaining by leaps and bounds, while their own situation is stagnant. That is bound to cause some bitterness. The people below are now providing competition that pushes down the cost of labor, both via outsourcing and immigration.