However, sewage treatment has many positive externalities as well, things not measured in market prices.

FORBES: Pollution Costs More Than What is Produced to Make the Pollution

At one point - not included in the edited interview - he mentioned "internalising positive externalities".

BBC: Is the eurozone crisis over? A central banker's view

When economists discuss rationales for government intervention in introductory economics courses, police services are sometimes offered as examples of goods that produce positive externalities.

FORBES: Pepper Spray Before Profits at UC Davis? Privatize the Police

You can see echoes of these sentiments in a recent blog post from Eli Dourado, where he urges everyone to create positive externalities.

FORBES: Economists and the Public Good

But they are not measuring the benefits of the positive externalities.

FORBES: Pollution Costs More Than What is Produced to Make the Pollution

Eli does take his own advice about creating positive externalities.

FORBES: Economists and the Public Good

Or as an economist might put it, if there are positive externalities generated by a business (good things for the wider economy for which the company doesn't receive direct financial payment), the chief executive is already being amply rewarded for them by a surplus element in his or her pay.

BBC: Do business leaders deserve their gongs?

To put it in economics terms, liberty produces positive--not negative--externalities.

FORBES: Uncommon Sense