Its the network effect, people gravitate to one location. SF & NYC benefit greatly from this. Chicago is nice, inexpensive, but sparse. Labor intensive operati

Its the network effect, people gravitate to one location. SF & NYC benefit greatly from this. Chicago is nice, inexpensive, but sparse. Labor intensive operations, like Groupon, benefit from Chicago because of the cost and availability of real estate. On the other hand, so does most of the rest of the United States.