What inning of the commodities boom are we in?

Commodities show clear price cycles, and for obvious reasons; even though over the long-term increasing supply has always won out over demand, in the short-term, demand is relatively inelastic and new supply takes a long time to come online. We are in year 5 of a commodity price boom every bit as spectacular as the one we saw in the 70's, and it's wise to question how long it will go on. Let's try to break down the forces at work here:

Supply -- prices for most commodities have been so low for so long that there's been very little investment in new supply. As a result, production and inventories are quite low. To get a handle on the future of supply, you would need to know:

• What level of prices justifies investing in new production?
• How sensitive are the price levels of other commodities to the price of energy?
  
• How long does it take to realize this production?
• How far along are we already in the process of expanding supply?
• What might the impacts of increased protectionism be on supply growth? Some commodity exporting countries are attempting to control exports and separate their domestic markets from the world market. The politics here feeds back unpredictably on the first question, of what price level signals to the market that new supply is profitable.
  

Demand -- commodity demand is clearly driven by economic growth minus the efficiency of that growth. Recently, the big growth in demand has come from the least efficient economies, namely China and India. In trying to evaluate whether this growth might soften, a few questions spring to mind:

• What percentage of demand growth has China represented over the last decade in each of the three main categories of commodities: energy, agriculture, and metals.
• What part of that emerging market demand growth was dedicated to feeding the never-ending desire for cheap plastic shit in the developed world. If we see a consumer led recession in both the US and Europe as the availability of credit declines, might this not curtail China's demand for commodities?
• What impact would it have if China became even marginally more efficient? Imagine if this efficiency came in the form of lower energy use per dollar of GDP. The resulting fall in the price of oil, might make the supply of all other commodities cheaper.