Index investing in the commodities market hasn’t done so well, according to an article in The Wall Street Journal.

The article cites data from Sam Stovall, chief investment strategist at CFRA Research, who said that since January 1970, investors who held the S&P 500 for at least 12 years would “always have had positive returns including dividends.” Commodity indexes, however, have not provided that type of return, says PNC investment strategist Amanda Agati, who argues that assuming such indexes will rise over the long term is a bad bet.

The article cites the following reasons:

• Unlike for stocks, technology has a deflationary effect on commodities—while innovation has driven big gains for tech companies and has even helped boost stocks outside the tech sector by improving companies’ productivity, “technology has generally had the opposite effect on commodities.”
• End users of commodities aren’t the same as buyers of stocks. While stock prices are “driven entirely by investors,” the article states, in the commodity markets participants include investors as well as producers and buyers of the commodities, and the actions of all of them affect prices.
• Commodities are cyclical by nature.
• Storage costs—when investors buy commodities, they can end up paying for storage and those costs can eat away at profits or deepen losses.