Must a market-based economy constantly expand? I vaguely recall from my reading of Adam Smith’s “The Wealth of Nations”, during college, that he opined that a market-based economy must constantly expand.  Is this recollection correct and, if so, what is the specific quote/reasoning?  Is it not possible for such an economy to be static and self-contained?
No idea who said that first, but I have seen similar assertions in economic commentary many times. The logic was never fully explained, but revolved around the notion that we need compunding income to pay compund interest. Authors treated the idea as so obvious or well known that they never saw the need to explain the details, or cite earlier authors. (It’s been awhile since I’ve seen the assertion, so I cannot give examples.)

In theory, the belief that the economy must expand appears incorrect. One could look at the various stock-flow consistent (SFC) models in “Monetary Economics” by Wynne Godley and Marc Lavoie, and one sees that steady solutions are easy to find. Although debt compounds, borrowers just pay down debt.

As a practical matter, the tendency is to prefer growth. However, in a services based economy, it is unclear whether real GDP growth gas to correspond to greater natural resource use, which creates a debate whether it is “real growth” or “paper growth.”