That's empty-world economics, and while that might have been fine for the 19th century and adequate for the 20th, we're living in an age where full-world economics is needed.
- Jake If you only spend 20 minutes of the rest of your life on economics, go spend them here.
Where the empty world assumptions comes around to bite the traditional marginalist economist on the buttocks is in dipping down into the conventional marginalist micro-economist to provide an underlying model of how hard or easy it is to achieve labor productivity gains. This activity goes under the heading of "putting the macroeconomic model on microeconomic foundations".
Even there, it is possible to assume absolute caps on material inputs, however it is analytically inconvenient, and the convention in traditional marginalist economics is to only assume analytically inconvenient things if absolutely necessary for the specific analytical problem at hand. Therefore the tacit presumption that there is an additional amount of material inputs available "at some price" is almost universally made, whenever the traditional marginalist economist is not explicitly considering a problem involving a resource limit. I've been accused of being a Marxist, yet while Harpo's my favourite, it's Groucho I'm always quoting. Odd, that.
Thinking of efficiency (output/input) in ecological terms, I would say it is fairly easy to estimate by looking at what is not output, that is waste. And our modern societies produce a lot which ends up as waste. Problably a world record in low ecological efficiency. The most ecologically efficient human societies would be those that has little or no waste, that is the societies we see as backwards and poor. A vote for PES is a vote for EPP! A vote for EPP is a vote for PES! Support the coalition, vote EPP-PES in 2009!
