First question:
When materials and technologies started to develop more, the global economy shifted slowly into manufacture. Because of the developments made, people were able to create more beneficial products for a cheaper cost in a shorter time span. And for this reason, manufactured goods rose above agricutural ones.
Second question:
In many areas of the country, there weren't enough jobs available for people. Because of this, many people were driven out to find other areas of the country to be able to provide for them and their families. This would increase the number of skilled workers in other areas and would also reduce the availablity of resources.