Which goods and services are best left to the market? And which are more efficiently and fairly provided as collective consumption goods by the state? This is at the heart of your revision of public goods. Central to your revision will be to understand why public goods may not be provided by the market. You can work this out by distinguishing between public and private goods and focusing on the ideas of rivalry and excludability in consumption. Students should understand the free rider and valuation problems – there are big debates in economics about the optimum size of the state. Rapid changes in technology are also changing the nature of what is and what is not a public good.