It isn't easy to figure out how many people you need for each construction. I've done the research for you.
 

Farms and Pastures

Pastures, farms, and other buildings don't have an apparent scaling system.
 
 
Pastures require only one worker. One worker can slaughter excess livestock. It is impossible to keep up with the number. This is especially useful for early game, when labourers may be scarce.
 
 
The variable for Farms is the time it takes to harvest before winter. For my games I use 8×8 farm plots. One worker is all that's needed to harvest everything in an 8×8. For example, an 8×16 requires two workers. Farms can be more productive if they have more labourers than needed. This is because the time it takes to plant and harvest is reduced. However, I found that this gain was marginal and not worth the cost of using up extra labourers.
 
If you have randomly-sized farming operations, then it is worth keeping an eye on them when the "time limit to harvest" warning pops up. Start with one worker (or a guess at it) and see how many plants are harvested before they die. If you observe any plants dying, increase the number to one.
 
The 'farming efficient' research increases harvest and planting by 100%. This is equivalent to adding one farmer.
 
 
 

Marketplace

Although the marketplace can be hard to see tangible benefits, it is my belief there are more workers in the marketplace that will lead to increased production elsewhere. With the delivery technology, increasing the workforce in the marketplace means that workers elsewhere will be able to work more efficiently as they don’t have to visit it as often.
 
 
I use it as a dump for spare labourers. Early game, I'll chuck any spare labourers in the marketplace if I have them. If I have labourer shortages, I will take them off to be used elsewhere. I gradually increase my number of permanent' employees as my population grows. The maximum 8 workers will be used when the market is at capacity.
 
 
 

Processing Buildings (Basically Everything Else).

The output of most other buildings increases linearly with the number workers. For example: I tested the output of a forester's hut or a gatherer’s hut with different worker numbers. The results were almost identical.
 
The same applies to most other buildings. You scale the number of workers based upon the output you require. You might need more soap than you currently have, so increase the workers.
 
 
Note: I haven't tried to determine if it is better having 1 worker in one building or 2 in another, but my research would indicate that it would be similar. Let me know if there is any other information.

 
 
And here is the end of the post, i hope you enjoy Settlement Survival – How Many Workers Do You Need? . If you believe we mistake something or we forget to add some content on the post let us know via Comment. The original post can be found here