In trading with each other cities can't be in too different stages of development, and they can't copy one another. Backward cities, or younger cities, or newly forming cities in supply regions, have to develop to a great extent on one another's shoulders. This is one of the terrible things about empires. Empires want them only to trade with the empire, which doesn't help them at all. It's just a way of exploiting them.
Jane JacobsI don't think that you can dispose of the constructive and inventive things that America is doing - and say, "Oh we aren't doing anything anymore and we are living off of what the poor Chinese do." It is more complicated than that. There is the example of Detroit which was once a very prosperous and diverse city. And look what happened when it just specialized on automobiles. Look at Manchester when it specialized in those dark satanic mills, when it specialized in textiles. It was supposed to be the city of the future.
Jane Jacobs