Things that can be consumed by everybody in a society, or nobody at all. They have three characteristics. They are: * non-rival – one person consuming them does not stop another person consuming them; * non-excludable – if one person can consume them, it is impossible to stop another person consuming them; * non-rejectable – people cannot choose not to consume them even if they want to. Examples include clean air, a national defense system and the judiciary. The combination of non-rivalry and non-excludability means that it can be hard to get people to pay to consume them, so they might not be provided at all if left to market forces. Thus public goods are regarded as an example of market failure, and in most countries they are provided at least in part by government and paid for through compulsory taxation. (See also global public goods. )