There’s also no natural law that says it needs to be stationary. The historical mean can just gradually rise. It can be like climate change. This is what makes markets fascinating — many independent agents evaluating the present opportunity set, acting on their internalized narratives and beliefs as well as data, with gradual turnover of the population of participants.

In a thread asking for options for present passive income (ie money coming in every month that you can eat with while you learn Python) it seems important to distinguish that need vs a long term investment strategy where you have money passively going out every month instead of coming in. One thing the market provides is a trade between people who have needs on different time frames.