Managing population fluctuations, both local and city-wide, is one of the biggest challenges of Banished. But with the right technique, it isn't one which can't be overcome.
When you need some household to migrate to another location, build a new house for them in the new location and just before the new house is finished, order their old house to get removed. They will then become homeless and migrate to the new house the moment it is finished.
Single households are in fact quite handy in this regard, because they give you a higher flexibility (you can move a single worker and don't have to move two at the same time). The downside is, of course, that more houses require more resources to build and more fuel to keep warm.
As a result of population fluctuations you will soon notice that workers who used to live close to their jobs will switch jobs and have suddenly a new job which is far more remote. To solve this issue you should regularly (every couple years) unassign all jobs by making everyone laborers and then reassign the desired number of workers to each occupation, starting with those where you consider proximity most critical. When you add a worker to an occupation, the laborer closest to an open job of that occupation will be converted, so by reassigning regularly you can re-optimize who does which job.
A ratio is not helpful because there are a lot of variables. Just like food, tools, and any other resource in the game, the real question is "How many people should I allocate to get the work done?".
Laborers pull work from the labor queue. The key to having enough laborers to work everything in the queue is managing that queue.
Scenario 1.
- allocate 4 builders and have 4 laborers.
- Command the gathering of resources from a large area.
- place two houses.
At this point, the labor queue has 3 things in it. Harvest resources, clear obstacles from build site, carry material to build site. Harvest resources was issued first, so the other two must wait. There are no build sites ready, so the builders act as laborers and go to the resource area. To fix this, use the priority tool on (the entire area of) the buildings. This causes the clear and deliver tasks to be done before the resource area task, and will cause the builders to build those houses sooner.
Scenario 2.
- Have a large city with farmers, miners, stoneworkers and very few laborers. Have enough of these workers that the resources they supply are usually at cap.
- Command the gathering of resources from a large distant area.
- Watch chaos happen.
When work is stopped for any reason, those assigned workers will pull tasks from the labor queue. In the first wave, farmers and miners will respond and make the journey to the resource area. During that first wave: your smith, tailor and woodcutter may need more material and so place actions at the end of the labor queue. Since those workers are out of material, they pull the top priority item from the labor queue and join the distant gathering. Now you have a tools, coats and firewood shortage.
Avoid this trap by not gathering large areas of resources at one time.
Best Answer
Not really, they're pretty dumb overall. You can however declare certain areas to be of high priority, making citizens focus on them over anything else (building a certain house, cutting a certain resource, etc).