23 In theory, the externalities of public goods and their nature as merit goods are the grounds for a universal service, but some argue that there is not necessarily a clear theoretical basis for determining the extent of externalities of individual public goods or whether or not they are merit goods (Refer to Clarke and Wallsten (2002)). For example, although a large number of developing countries have positioned the use of the telephone line network as a universal service, many of them still have not guaranteed their citizens sufficient access to medical care, a service which is thought to have stronger merit good characteristics.