Definición de "una economía"

El New York Times ha convencido a Paul Krugman para que responda a algunas preguntas de Economía que libremente le formulen los lectores en su blog. Entre las preguntas y respuestas que más me llaman la atención está "la definición de lo que es una economía" (la letra en negrita es mia):

PREGUNTA DEL LECTOR:

From a “martian-looking-down-at-earth” perspective, what exactly is an “economy?” How would you sum it up? What alternative ways could we conduct our societies that might work better if we could start from scratch? What do you think is going to work in 10, 25 and 50 years that we are not doing now?

RESPUESTA DE PAUL KRUGMAN:

I guess I’m a bit boring on such issues – I don’t have any deeply unconventional insights. I’d say that the economy is everything that involves making or using goods and services. That means leaving out subtler things like love, faith, and culture. (Alfred Marshall described economics as being the study of the “ordinary business of life.”

I’m also fairly conventional on how economies should be run. Self-interest is still the best motivator we know – or more accurately, the only consistent motivator. So I’m for market economies. But I’m for market economies with strong safety nets, with adult supervision in capital markets, with public provision of goods the private sector does badly (like basic research and much of education.) An idealized New Deal is about as far as I go.