[curiousgeorgio]

If Philly is where our industry is, then we only need as many people to live in Philly as the labor market demands. However, if unemployment is high or wages are too low (relative to the cost of living) in an area, then that suggests we have an oversupply of labor there, not a shortage. Basic goods (food, clothing, materials for housing) are grown/produced in many areas (even rural ones), not just in dense cities, so no, transportation costs don't really increase the cost of living in rural areas. To the contrary, in most cases it's far, far cheaper to live outside of dense cities.