|By shared global challenges, this evaluation refers to what economists call "global public goods." Typically, public goods are defined as those goods that are both "non-rival" (you or I or both of us can consume the good without affecting the utility either of us derive from its consumption) and "non-excludable" (once the good is produced, no one can be prevented from enjoying it). A slice of cake is a private good because it does not manifest either of these principles: if I eat the cake, you cannot; once the baker bakes the cake, she can prevent you from eating it unless you pay for it. By contrast, an effective local police force is a public good. You and I and all the residents of a town can enjoy physical security on the streets simultaneously; once the police establish security, they cannot exclude anyone from enjoying it. Global public goods, of course, also have a spatial dimension, and so include only those issues that are trans-border in nature.
In its strategy for addressing global public goods the World Bank identifies five areas of global public goods for its engagement. These include the environmental commons (including the prevention of climate change and biodiversity), communicable diseases (including HIV/AIDS, tuberculosis, malaria, and avian influenza), international trade, international financial architecture, and global knowledge for development.