The three fundamental components of food security, availability, access and utilization differ in urban and rural contexts and across urban socio-economic groups. A greater diversity of both local and imported food products are available in cities although, most of the food is not produced within city boundaries. Access to food in urban areas is dependent on cash exchange, with some exceptions where some urban food production contributes directly to household intake. Reliance on purchased food is the leading factor in household food security of poor urban populations, yet many lack a fixed income. Many households use urban agriculture as a means of supplementary income and for direct household consumption, although these activities are often discouraged by municipal authorities.