They form isolated communities in inner-city slums or on the outskirts of growing cities, without access to services and with limited access to the formal labour market. Cities fail when they do not address equity. Without strong institutions, effective health and social networks, fair wealth distribution and a safe and clean environment for living and working, population's distrust in institutions grows, disparities increase, violence increases and new economic investments do not occur. When they succeed, cities are prosperous for all.