Two sets of graphs here, "all available data" and a shorter term two years of data.

Very short summary:

• positions may not be considered as an homogenous quantity. Each commodity is different and all have a different population of traders:
  - plain purchasers actually buying future deliveries, or hedging (IMO the true "commercials"
  - long term speculators
  - extra-market spreaders, one commodity against another, even on different freign markets - ...
• long term hedgers (as some gold companies), carry trade coverings, ...
• seen on a long term, there is a correlation between the total open interest and the prices
• we have to find a way to differentiate pure speculation (which effectively moves the prices) from long term trends.
• one attempt is the plotting of the "net commercial shorts" positions which will be corrected or not by a formula of sorts
• in most cases, when "net commercial shorts" increase (become more negative), this is not a result of a plot. As the total of shorts equals the total of longs equals the open interest, any long position of a speculator MUST be met by an increasing number of commercial short positions. Hence, increasing net commercial shorts is the representation of increasing speculative longs.