As an economist trained in the neo-classical tradition, I am constantly on the lookout for market failures. Externalities are a reliable source of market failures and when I come across a positive externality, I get a warm and fuzzy feeling. Consider a story that exhibits the benefits of positive externalities.

From The Economist (9th Oct 2003) an article on the perceived corruption of countries.
Finland remains the least-corrupt country in the world, according to the latest annual index compiled by Transparency International, a Berlin-based organisation. The index, which measures perceived levels of corruption, focuses on the misuse of public office for private gain. The United States ranks as the 18th least-corrupt country, only a little less so than Chile. Botswana is reckoned to be less corrupt than Italy.
India ranks 83 in …