Well don't know this Daniel Vergin, but I figure he's an economist. They tend to think that more money and new technology create more supplies. Economic models don't take depletion into account.
There'se a very interesting article coming out in Energy Policy
The mineral economy: a model to for the shape of oil production curves
Ugo Bardi
Dipartimento di chimica, Universita de Firenze, Italy
He used a very interesting stochastic computer model. He considered an island with a certain population. The island has no natural foodsource. Instead the islanders are living on cans of hardtack which were once washed ashore and buried under the sand.
Now the model is very simple. The islanders have to find the cans to survive and to multiply. If they don't find the cans in time they die and population decreases. You can further complicate the model by introducing various factors such as clustering of the cans, introducing a certain time laps between the find and production, introducing production costs and prices etc.
Now the most interesting part is the production curve. Under unconstrained conditions you get an ideal Hubbert type bell shaped curve.
When introducing technology (making the islanders more efficient in finding hardtack over time) the curve becomes asymmetrical. However the
peak production comes earlier (not later) and the drop-off is steeper(!!!!!!!!!!!). Introducing technology will enhance population growth and consumption thus accellerating depletion.
The only thing that delays the peak is conservation. If the islanders store some of the cans and limit population growth the curve swings the other way.
Now this work has been peer-reviewed, and I think it's a sound representation of a mineral source under depletion. It also gives scientific backing to Hubbert's empirical curve. It makes you understand why it has to be bell shaped.
Its a hell of a link I hope it works. I'm sorry I can't provide you with the complete article, but Elsevier is quite strict with illegal copying and I don't want to lose my subscriptions.
http://www.sciencedirect.com/science?_o ... f84c2416c9