Yes, the middle income bracket is shrinking. The lower income bracket is growing. Even outside of SV wages have stagnated in the lower tiers (since 1974 in varying degrees.)
(edit) I should add this is by percentage. A recent study says the percentages have stabilized for now.
(edit) I should add this is by percentage. A recent study says the percentages have stabilized for now.
http://www.pewresearch.org/fact-tank/2018/09/06/the-american...