Well, there are some, you will find Ralph’s all over Los Angeles. But why aren’t there more? (This query is posed here, here, and here, among other places.) Factor #1 in my view is lack of cars. Living in an inner city has its downsides, to say the least, but at least you don’t have to buy a car. Yet the modern grocery store is designed for car transport, both how you get there and how you get the groceries away and of course the radius of advertising. With fewer cars per capita the tendency is for smaller, more local stores, which is precisely what we see in poor neighborhoods. Not surprisingly poor people are most likely to have cars in LA, and thus most likely to have grocery stores there as well. For that matter real grocery stores are not all that common in wealthy but relatively carless parts of major cities, such as Manhattan.
Crime is surely a factor as well, what do you all think and what other natural experiments come to mind?