I am in Toronto, Canada. Marine Technics Ltd. Radioequipment, ship spare parts, etc. A eto to tschislo, k kotoromu wy daete otwet na wse woprosy. Collin Dear Alfred Koh, I disagree with your view that geographic stratification of cities will increase security.
Stratified city is a time bomb for social onflict.
All stratified American cities experienced that conflict in form of riots many times. European cities are on the other hand very homogenious. Of course, there are poorer and richer neighborhoods everywhere, that's expected, but there aren't outright ghettos. Hense no riots, no social conflict.