Earlier quoted context omitted.
> But there were not many orcs and goblins for a long time in many areas, as we learned from the books. They only came back and multiplied with the slow return-growth of Sauron. Sauron had already returned c1000 TA to Dol Guldur. We're specifically told that evil things, such as Orcs, begin multiplying in number by c1300 TA, which triggers the migration of the Hobbits to the Shire (already we have an example of why t…
Wars and plagues every couple hundred years or so. So what you are saying is that wars and plagues are significantly less frequent then they were in pre-industrial Earth.
One of the more common last names in Norway is still "Ødegaard", literally "Deserted farm", reflecting families who were residing on farms which still had not gotten a proper name by the time the tradition of using your fathers first-name as a last time started dying out. This even then - by the 1800's - involved re-clearing farms that had still not been re-settled after the Black Death.
Of the ca. 36500 farms which existed in Norway around year 1300, only about 16000 were still populated by 1520, and the population is believed by some sources to still have been only half of what it was in 1300. It was not until the 17th century that Norway "recovered" - that is, until it was back to pre-plague, levels, having lost several centuries of growth, but with population centres having changed, leaving many ancient farms still empty reminders.
In Norway, a disproportionate portion of the political and religious elite died. E.g. while almost the bishops in Sweden survived, all but the bishop of Oslo died in Norway. The Northern provinces of Norway were left to their own devices for a long time, without a functioning government, because so few government officials were left that the king chose to focus restoration in the South and largely just abandoned them.
That was one event.
I also don't recall running into Nazgul and Orcs while growing up near Oslo, and imagine facing that might have been a rather severe deterrent to growth.
EDIT: I'll add that Norway is a good reminder that a combination of destructive events, harsh conditions and the extremity of the hockey stick nature of population growth can explain a lot. Norway today has a population density of ~14 per km^2. In 1950 that would've been ~8. In the mid 18th century about ~3. In the aftermath of the plague, likely <1, and still <1 by the 16th century. You can still travel on foot for days through central Norway without meeting people if you stay clear of the places most popular with people out hiking for fun. A couple of centuries back, and not only would you be able to do that, but you'd have been likely to now and again come across farms that had been empty for centuries, despite centuries of a growth and recovery.