Some investors in the oil market lost big as they danced the contango in 2010. Owners holding shares of the United States Oil Fund (NYSE:USO) actually lost 0.7 percent even though front-month WTI prices rose 15.2 percent on the year. USO’s contango-resistant sibling, the United States 12-Month Oil Fund (NYSE:USL), fared better by wringing out 6.5 percent in capital appreciation against the stiff carrying-charge headwind.

Last year, the average cost for a three-month NYMEX WTI crude oil roll was $2.27 a barrel. While that’s a pretty steep price to pay for staying in the market, it’s actually an improvement. Since WTI flipped into contango in June 2008, the average quarterly roll cost has run up to $2.97.

For a commodity like oil, the size of the spread between futures deliveries is an indicator of supply. When demand is slack, or supplies more than plentiful, there’s oil to carry into storage. The costs of carrying that oil are reflected in deferred delivery prices.

In better economic times, demand for oil heightens and above-ground stores tend to be drawn down. That narrows the market contango and, at times, even flips the futures curve into backwardation. In an inverted market, near-month prices rise above those for distant months, reflecting the bidding for more immediate deliveries. The WTI market was, in fact, inverted for more than 10 months before prices tumbled in the summer of 2008.

Traders often capitalize upon the changes in the futures curve with spreads. In a spread, a trader buys an oil futures contract and simultaneously sells a contract deliverable in a different month. A trader expecting higher prices (implying tighter supplies and a smaller contango) would likely buy a nearby delivery against the sale of a more distant contract in the expectation of a narrowing contango.

A bear spread—short the nearby, long the distant contract—would be the trade of choice when oversupply and lower overall prices are expected.

The expansion and contraction in oil spreads has left some readers puzzled when they regard a seemingly different pattern in the gold market.

Particularly noted was the recently tumble in gold prices as funds sold their positions to rebalance their portfolios and unwind late-year window dressing. In response, gold spreads, i.e., contango, actually shrank—the opposite of what would be expected in the oil market.

The reason for this is simple: gold is different.

It goes back to supply and demand. Unlike oil, there are large stocks of gold above ground. Above-ground supply constantly builds because gold isn’t consumed, so price fluctuations don’t tend to reflect near-term tightness or surplus, but rather, the market’s changing perception of its value. You don’t see backwardation in the gold market as you do in the oil trading ring. Nearbys almost always trade at a discount to distant deliveries.

Gold spreads are more sensitive to changes in carrying costs, the most significant being interest rates. In a bear market, the premium in a back-month contract shrinks because lower prices imply a lower financing cost component in the contract’s total value (the other carrying charges—storage and insurance—are stickier).

A bull market is characterized by a widening contango.

Thus, in a bear market, gold spreaders—as a proxy for outright short positions—will tend to short forward contracts while buying nearbys.

Gold watchers should keep an eye on gold spreads to gain insight into traders’ mentality and overall market sentiment.

Written by Brad Zigler From Hard Assets Investor

HardAssetsInvestor.com (HAI) is a research-oriented Web site devoted to sharing ideas about hard assets investing. The site has been developed as an educational resource for both individual and institutional investors interested in learning more about commodity equities, commodity futures and gold (the three major components of the hard assets marketplace). The site will focus on hard assets investing without endorsing or recommending any particular investment product.

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