What makes something a commodity?

By H.T.

To mark the publication of "Go Figure", a collection of The Economist’s explainers and daily charts, the editors of this blog solicited ideas on Facebook and Twitter. This week we publish five explainers suggested by our readers, who will each receive a copy of the book.

A COMMODITY, said Karl Marx, “appears at first sight an extremely obvious, trivial thing. But its analysis brings out that it is a very strange thing, abounding in metaphysical subtleties and theological niceties.” A commodities trader might snort at such a definition: there is nothing much metaphysical, after all, about pork bellies—however divine (or sinful) the taste of bacon. Yet for thousands of years, from rice in China to gold, frankincense and myrrh in Biblical times, to spices in the days of empire, they have been the building blocks of commerce. At the peak of the China-led super-cycle in 2011, they accounted for one-third of the world’s merchandise trade. They encompass an array of materials—from food and flowers to fossil fuels and metals—that appear to bear little relation to each other. What makes something a commodity?