This isn't really a question, so much as me wondering if anyone else has encountered this weird issue.

So, in 2 separate games, one that was a thriving trade port and one that went total isolationist, at around 200-250 people there is a significant drop in birth rates. the first town this happened to had a fire and so promptly got abandoned after the entire town burnt down while there were 30 free laborers with max priority on the fires and wells and water everywhere...but thats a discussion for another day. but I'm currently playing the isolationist one and I got to around 220 people, built 5 new houses which people moved into, then promptly saw the birth rate decline by half and over the course of the next 10-20 years saw the population reduce all the way back down to 180, where it is normalizing and starting to grow again.

in both cases I had sufficient food for everyone, more than enough firewood/coal/coats, full 5 star happiness and 4-4.5 star health ratings. until the end of the population decrease in the town that survived anyway, when the number of adults in town dropped from 180 at its peak to 120 and I have to do some wicked maneuvering of manpower to keep food production and warmth production at sufficient levels to keep everyone alive. this is the most painful thing I've experienced in the game other than fires, and I've had direct hits by tornados, plague outbreaks, infestations, and mass random death by environment (rocks falling/cave-ins/trees falling/you name it).

Has anyone encountered this before, and if so, is there anyway to combat it besides building way more houses than you feel comfortable with?

I've had something like this happen before and it was because I waited too long to expand my village and most of the people I had moving into new houses were already over the age where they stop having children. Around 40 years old. This can make your population drop off pretty fast once the older people start dying off and there's no young couples to replace them.

The easiest way to avoid this seems to be trying to keep your student/child population around half of your adult population. Start checking your houses, if you've still got some relatively young people living with their parents, build some more houses so they can move out and start breeding like crazy (hopefully).

If not, make sure you've got a town hall, trading post, and market and maybe you'll get a large influx of nomads to help you start rebuilding your population again.

I'm not sure if it's possible to counter the population waves without always putting down houses at precise times. It seems like it's just something that happens if you stop expanding. So long as you have expanded enough by the time your first generations die off the waves are usually manageable.

I kinda hope the dev tweaks this part of the game, because it is quite annoying if you just want to slow down town expansion for a while.

ah, yeah, that makes sense. thanks for the info. I thought I was expanding pretty consistently, but I probably took like 2-3 seasons off at some point because I was fixing my food situation for the next wave. It does seem like its punishing you for not expanding at the absolute perfect time, because the only time I've had really good steady growth is about when I hit 270+ and that just backfired intensely on me because I didn't notice my 25k food reserves going down by like 3000 a season until it hit 12k and I couldn't build fishermen/gatherers/hunters/etc fast enough to fix it before losing like 100 people to starvation. so now I'm all the way back down to 220. time to start building up again and hopefully with enough food production to actually sustain my town! yay

Oh, and for the surviving town I refused to get a trade post until I hit 300 so I could get the achievement, and nomads don't show up until you have one, so I was rebuilding my numbers very slowly for a while. and after building my trade port the first group of nomads to approach me was a group of 75. I don't think I'll ever want nomads numbering more than 50 because I've had 25 nomads come in and wreck a growing economy, 75 would just destroy everything.