[PaulRobinson]

Consider how big the difference is between each segment identified here. Realise that the upper income bracket itself could be broken down into three segments that would show an ever starker difference.

Unequal gains is the problem, and your intuition can help inform why: the 2023 dollar index used is based on what rate of inflation? CPI? RPI? Something else? Why is it that in 1970 a median income household could buy a home on a single income and raise a family (including sending kids to college), on a 2023-dollar income of $66k, but that's mostly not possible on $106k in actual 2023 for most households.

When you adjust for real buying power using a less favourable means of assessing inflation and taking into account housing costs more fully, I sense you'll find that the bottom two brackets are behind their 1970-adjusted counterparts, and the upper income bracket is significantly better off, especially if you then break that upper segment up a little into more categories.

And, without something happening to adjust this, the effect is going to just get worse and worse, and everyone knows it.

[renewiltord]

Well, housing is obvious. It's because most Americans are eager to have community (by which they mean suburban homes) and a short commute and a separation between commercial and residential spaces. This is a process that clearly yields outcomes that are not time-invariant. In the same sense that asking "why did people back then get to put a house down near Golden Gate Park and I don't?" is meaningless. Because eventually all the places near GGP have houses.

As Adam Driver points out in Ferrari, "two objects cannot occupy the same place at the same time". A view some might find counterintuitive.

[discodonkey]

It seems to be using the CPI. The basket of goods & services the CPI is referencing is determined by the extensive Consumer Expenditure Survey, and reflects to a fair degree the actual spending habits of Americans.

Obviously, if you give more weight to housing, you're going to get different results. But it would distort the actual change in expenditure.

[xracy]

Why wouldn't you include housing? It's often people's largest expense?

[renewiltord]

What makes you believe that housing is not included? Consider using a search engine (Google is pretty good) and using keywords like "cpi shelter weight" or "cpi housing weight". The BLS has a page on the subject.

[xracy]

Sorry, I read the 2nd sentence as removing housing entirely, for some reason. I see that's not what they're saying, they're just talking about the relative weight of the thing.

My apologies for not knowing offhand everything that goes into the CPI, and not googling it for more context, I was just asking questions on the internet instead. I should've known better than to hope for learning something from my fellow humans.