“Upper middle class” has nothing to do with it.

In 1950, the median household could buy a house with 2 years of income. That is, 50% of households could do this.

Today, the median house costs $400k. Only the top 12-14% of households make 200k per year.

So proportionally, the % of households that have the same buying power as a median 1950s household has shrunk roughly 4x.

Those do not measure the same thing.