In the middle ages, most people grow their own food in the fields and produce little surplus for sale. If you move to the city, you have to find a job, earn money and buy, not grow your own food, you are then subject to economic conditions, but for the subsistance peasant farmer, it really doesn't matter that the economic conditions are, your overlord taxes you in kind, not in coin, so if he requires 20% of your crop, you give him 20% of your crop and keep the other 80% to feed your family with - that is how feudalism works, its all about feudal obligations and loyalty oaths, money is scarce, and most trade occurs using goods as a medium of exchange. The unemployment rate doesn't matter to the peasant growing his own food, but it does matter to the city-dweller, he can't grow his own food there. There needs to be a powerful reason to get that peasant off the farm where he has guaranteed lifetime employment and into a city looking for work, since most peasants can't find that reason in the middle ages, most stay on the farm and a small minority live in cities, thus cities are very small. 90% of the population live in the countryside where they can grow their own food, they make their own clothes, and that they cannot make they trade for, sometimes a skilled craftsman is called for, but they are not often required by most people.