Oh yeah recessions happen in SC for a number of reasons. I'm not sure about a depression though, it seams like many players would have to forcefully educe a depression.
What I think your referring to an individual demand/supply of one/possibly several good/s, not a decline in economic growth of the world/country/region (basically what a recession is). Probably the best way to determine economic growth in SC is to check the demand history of production plants, each increase of production plant equals a new corporations built, if demand is steadily increasing then economic growth is increasing (well technically, if you count military industrial complexes a real determination of the global economic growth), if demand has decreased significantly then its probably a recession. LU just recently went through a recession (or maybe even depression) because of world wide HLW shortages, which resulted forced me to close 2/3 of my production plant corporations. I'd say now LU is still slightly in recession or recovering.
Here is a thread which may answer your question
https://www.simcountry.com/cgi-bin/discus/board-auth.cgi?file=/6/9481.html&lm=1214897935