I sometimes hear the claim that innovation in the physical world has stagnated since around 1970. More specifically, chapter 1 of The Rise and Fall of American Growth by Robert J Gordon claims that there has been basically no innovation in clothing other than changes in fashion. This is somewhat contrary to my intuition (although I definitely believe that innovation in the 50 years before 1970 was greater that in the 50 years after), and price of insulation seems like a relatively objective metric for this.
My favourite type of response would be time series data of clo per inflation-adjusted dollar, but I'd also appreciate people's subjective experience of this.
On Facebook, Stefan Schubert linked to this CPI chart showing that the price of clothing has declined relative to the prices of other things over the past 20 years.