It may be appropriate and relatively easy to distinguish between investors and speculators in financial markets. However, no matter how the terms are defined, it is impossible to separate them in commodity markets.

Historically speaking, investors have been thought of as pursuing a noble purpose – putting capital into a business or activity for profit and the common good. Conversely, there is a long history of speculators being portrayed as villains who reap “ill-gotten” gains at the expense of the poor and unfortunate. This distinction is carried forward in the language of modern politics. The Dodd-Frank financial legislation of 2010 was in part designed to punish those speculators blamed by politicians for causing the...