Underpaid/free labour (by women and black) that was very common back then. Much less now. This sosiety shift alone could double every price in economy, while keeping wages stagnant.
If people were underpaid back then, wouldn't the average salary have raised significantly over the past decades? However his article shows that it's pretty much stagnant.
wouldn't the average salary have raised significantly over the past decades?
Not if those people were previously excluded from salary calculations. If they were unpaid, it's definitely true that they weren't included in the average salary figures.
I.e. household income rose even if wages did not.