And the main factors contributing to financial stress for the six-figure set include inflation, economy-wide instability, interest rates, and a lack of savings.

Source: https://www.breitbart.com/clips/2023/04/12/cnbc-majority-of-people-making-over-100k-say-theyre-financially-stressed-inflation-is-top-cause/

Thus, in such a context, material efficiency would be reflected in the reduction of materials used in automobiles and most precisely in the economy-wide quantity of materials used in passenger kilometers traveled.

Source: https://www.forbes.com/sites/saleemali/2023/12/27/lonely-crowds-and-a-greener-sharing-economy/