Oh get off your tiny America centric soapbox.

Post WWII incomes soared because the western victor nations were the only ones with advanced manufacturing capabilities left after the war.

They utilised the raw resources of the developing nations to do the value-add manufacturing, and got rich. During these years the 5% of the worlds population in those few nations was reaping 30% of the worlds income. Even the working class gets a good deal when you have that few people getting that much of the world's loot.

Now this wealth is shared with the growing middle classes of the more recently developed nations - Korea, China, India, and many SEA nations.

Post WWII being a reasonably educated worker in a nation with industrial capacity was special, and so you got paid well.

Now it is not special. Many countries, with millions upon millions of people, meet these conditions, and so such skills cannot demand such a wage.

Now, yes, Income inequality IS A MASSIVE SOCIETAL ISSUE, but it is not the one driving down blue collar wages - That is simple demographics.