why (and why not) to invest in commodities

A couple years ago I wrote a cautionary post in the wake of the run-up on gold over the past decade. Since then, gold has…well, not gone really anywhere, and neither have commodities in general. So I figure now is a good time to talk about investing in commodities, when people aren’t jumping up and down about how they’re going through the roof (or the floor).

Don’t speculate on commodities. Well, I don’t recommend speculating on investments, ever, but it’s especially true for commodities. You think the stock market is a roller-coaster ride? Commodities will make you lose your lunch! Remember back in 2008-2009, when the S&P 500 got cut in half? GSG, an ETF that tracks the S&P Goldman Sachs Commodity Index, plummeted by two-thirds, and it’s hovering at around half of its 2008 high even today. Yes, the runup on gold since 2000 is drool-inducing, but so were internet stocks before 2000 and real estate before 2008. Don’t become yet another cautionary tale.

Don’t look to commodities to boost your returns. “OK, fine — I’m investing in commodities for the long term. They’ll make me rich!” No, they won’t. By definition, commodities are items that can be replaced. Any time any given commodity gets too expensive, corporations start figuring out how to do without it — witness the explosion in hybrid technology when oil prices were shooting up a few years ago, or the move to copper wiring by companies that traditionally use gold. No, over the long term commodities barely keep up with inflation — no surprise, since the price of commodities is pretty much the definition of inflation. (Gold has historically been no exception…which should make current holders of the shiny stuff very cautious when looking at charts like this.)

Don’t invest in commodities as your primary hedge against inflation. Afraid of inflation? Invest in Treasury Inflation-Protected Securities! While they have normal interest just like any other bond, their principal is adjusted for inflation, which makes TIPS a safe, low-volatility way to guard against inflation. (By design, their yield is exactly their inflation-adjusted return!) While commodities track inflation over the long term, they may go for years before reverting to the mean; in mathematical terms, they have a positive but lower correlation with inflation than TIPS.

Do invest in commodities to reduce your overall portfolio volatility. Commodities are very interesting in that they don’t often move in tandem with either stocks or bonds. This means that, with regular rebalancing, a canny investor can take advantage of commodities to smooth out their portfolio, selling commodities when they are high to buy stocks and/or bonds, and vice-versa, with the overall effect of reducing volatility. Now, note that I said “don’t often move in tandem”; in 2008, they crashed along with nearly everything else, so don’t look to commodities to work miracles. That’s the job of short-term treasuries!

So yes, commodities can be a useful part of your portfolio, if bought for the right reasons. Next stop — how (and how not) to invest in them!