I list agglomeration benefits from my study notes (Urban economics). * Knowledge spillovers. This core idea for information-based agglomeration economies. Rob

I list agglomeration benefits from my study notes (Urban economics). * Knowledge spillovers. This core idea for information-based agglomeration economies. Robotics researcher benefits from touching randomly elbows with metallurgy expert and vice versa. Random human contact happens in internet too, but you don't form deep connections as a rule. Has anyone had a hours long beneficial discussion with random guy in the internet? * Labor market pooling allows labor to be more efficiently allocated following productivity shocks. Changing jobs is easier. The ability to switch into a new job is first order agglomeration benefit. When large number of similar jobs are located at the same area, its easier for people to change jobs and find the job that makes them most productive. * Marriage multiplies the effect of labor market pooling. When people marry each other and move together they must find a two jobs within working distance. If they are both highly specialized, highly educated or both, only largest cities allow best job for both without sacrifice. * Services and more choices. Even a Pizza delivery guy can be more productive in dense city. That justifies the little higher salary for pizza delivery guy. There is more different services available. Increasing the value of the location. * coagglomeration. The tendency of industries to colocate with other industries and form tight networks that respond fast to new demand. * Cost of moving people. Travel time reduces productivity significantly. * Logistics in general is and faster and more efficient. Benefit of moving goods is now considered relatively second order. * Congestion has costs. Pollution and expensive housing are results of failing urban development. Without congestion costs the concentration of people into the best cities would be even faster.