Africa best places to visit for As with other economic activities, services can be measured either on the demand side, as a share of aggregate consumption, or on the supply side, as a share of aggregate production. Since there is no generally accepted definition of services, the service sector is notoriously difficult to demarcate regardless of the method. This is why the service sector, as the tertiary sector, is often simply seen as the residual economic activity after the primary (agriculture and extractive industries) and secondary (manufacturing) sectors have been defined. One consequence of this categorization is that activities comprising the tertiary sector are extremely heterogeneous. The process of tertiarization, i.e., the rapid growth of the service sector at the expense of the primary and secondary sectors in practically all (and particularly in the most developed) economies, makes the absence of clear sector definitions an unwelcome fact. Africa best places to visit 2016.