International Public Goods (IPGs) achieved prominence with the United Nations Development Programme's publication Global Public Goods  (Kaul, Grunberg and Stern 1999).  That study included a wide-ranging definition of IPGs that encompassed a broad range of development activities. Analytically, that definition has since been narrowed by, for example, Kanbur, Sandler and Morrison (1999). Operationally, the World Bank has further distinguished between core and complementary activiities associated with the provision of IPGs. The essential point here is that IPGs provide widely available benefites, and providing these benefits is the core activity. However, helping people or countries actually avail themselves of the public goods (to consume them) may also be necessary. Such expenditures are complimentary to the core activities.

In this chapter, we attemopt to pull together current thinking on an appropriate delineation of IPGs. Our goal, in part, is to provide a basis for a chapter 5, which quantifies the extent to which donor aid has been provided to financed the provision of public goods. What exactly are IPGs? How can we assess whether official development assistence is succeeding in providing them? This chapter first attempts to define public goods, then clasifies them according to the types of benefits they yield from the persepctive of users, and finally relates these categories to sectoral expenditures that are most likely to provide benefits that have an international scope. We also discuss some implications for the financing of IPGs, in particular, the nature of cost sharing arrangements that may be reasonable when the citizens of different countries value the same public good very differently.