(Bloomberg Prophets) —Profiting from commodity trading often requires a combination of market knowledge, luck, and most importantly, strong risk management. But the number of commodity trading houses has dwindled over the years, and the institutional, pure-play commodity hedge funds that remain — and actually make money — can be counted on two hands. Here is a list of some of the larger commodity blow-ups:

1990

Phillip Brothers

The largest and most successful commodity trading house in its day caved, triggered by copper trading

1993

Metallgesellschaft AG

The New York branch of this large German conglomerate lost $1.5 billion in heating oil and gasoline derivatives

1995

Sumitomo Corp.

Yasuo Hamanaka blamed for $2.6 billion loss in copper scandal

2001-2002

Enron Corp.

Dissolves after misreporting natural gas trades, resulting in Arthur Andersen, a ‘Big 5’ accounting firm’s fall from grace

2005

Refco

Broker of commodities and futures contracts files for bankruptcy after accounting fraud

2006

Amaranth Advisors

Energy hedge fund folds after losing over $6 billion on natural gas futures

2011

BlueGold Capital

One of the best-performing hedge funds in 2011, closed its doors in 2012, shrinking from $2 billion to $1.2 billion on crude oil bets

2014

Brevan Howard Asset Management

One of the largest hedge funds globally. Closed its $630 million commodity fund after having run well over $1 billion of a $42 billion fund

2015

Phibro

The sister and energy trading arm of Phillip Brothers, ranked (1980) the 15th largest U.S. company, dissolves

2015

Vermillion Asset Management

Private-equity firm Carlyle Group LP split with the founders of its Vermillion commodity hedge fund, which shrank from $2 billion to less than $50 million.

Amid the mayhem, banks held tightly to their commodity desks in the belief that there was money to be made in this dynamic sector. The trend continued until the implementation of the Volcker rule, part of the Dodd-Frank Act, which went into effect in April 2014 and disallowed short-term proprietary trading of securities, derivatives, commodity futures and options for banks’ own accounts. As a result, banks pared down their commodity desks, but maintained the business.

Last week, however, Bloomberg reported that Goldman Sachs was “reviewing the direction of the business” after a multi-year slump and yet another quarter of weak commodity prices.

What happened?

In the 1990s boom years, commodity bid-ask spreads were so wide you could drive a freight truck through them. Volatility came and went, but when it came it was with a vengeance, and traders made and lost fortunes. Commodity portfolios could be up or down about 20 percent within months, if not weeks. Although advanced trading technologies and greater access to information have played a role in the narrowing of spreads, there are other reasons specific to the commodities market driving the decision to exit. Here are the main culprits:

Low volatility: Gold bounces between $1,200 and $1,300 an ounce, WTI crude straddles $45 to $50 per barrel, and corn is wedged between $3.25 and $4 a bushel. Volatility is what traders live and breathe by, and the good old days of 60 percent and 80 percent are now hard to come by. Greater efficiency in commodity production and consumption, better logistics, substitutes and advancements in recycling have reduced the concern about global shortages. Previously, commodity curves could swing from a steep contango (normal curve) to a steep backwardation (inverted curve) overnight, and with seasonality added to the mix, curves resembled spaghetti. Correlation: Commodities have long been considered a good portfolio diversifier given their non-correlated returns with traditional asset classes. Yet today there’s greater evidence of positive correlations between equities and crude oil and Treasuries and gold. Crowded trades: These are positions that attract a large number of investors, typically in the same direction. Large commodity funds are known to hold huge positions, even if these only represent a small percent of their overall portfolio. And a decision to reverse the trade in unison can wipe out businesses. In efforts to eke out market inefficiencies, more sophisticated traders will structure complex derivatives with multiple legs (futures, options, swaps) requiring high-level expertise. Leverage: Margin requirements for commodities are much lower than for equities, meaning the potential for losses (and profits) is much greater in commodities. Liquidity: Some commodities lack liquidity, particularly when traded further out along the curve, to the extent there may be little to no volume in certain contracts. Futures exchanges will bootstrap contract values when the markets close, resulting in valuations that may not reflect physical markets and grossly swing the valuations on marked-to-market portfolios. Additionally, investment managers are restricted from exceeding a percentage of a contract’s open interest, meaning large funds are unable to trade the more niche commodities such as tin or cotton. Regulation: The Commodity Futures Trading Commission and the Securities and Exchange Commission have struggled and competed for years over how to better regulate the commodities markets. The financial side is far more straightforward, but the physical side poses many insurmountable challenges. As such, the acts of “squeezing” markets through hoarding and other mechanisms still exist. While the word “manipulation” is verboten in the industry, it has reared its head over time. Even with heightened regulation, there’s still room for large players to maneuver prices — for example, Russians in platinum and palladium, cocoa via a London trader coined “Chocfinger,” and a handful of Houston traders with “inside” information on natural gas. Cartels: Price control is not only a fact in crude oil, with prices influenced by the Organization of Petroleum Exporting Countries but with other, more loosely defined cartels that perpetuate in markets such as diamonds and potash. It’s downright difficult: Why was copper termed “the beast” of commodities, a name later applied to natural gas? Because it’s seriously challenging to make money trading commodities. For one, their idiosyncratic characteristics can make price forecasting practically impossible. Weather events such as hurricanes and droughts, and their ramifications, are difficult to predict. Unanticipated government policy, such as currency devaluation and the implementation of tariffs and quotas, can cause huge commodity price swings. And labor movements, particularly strikes, can turn an industry on its head. Finally, unlike equity prices, which tend to trend up gradually like a hot air balloon but face steep declines (typically from negative news), commodities have the reverse effect — prices typically descend gradually, but surge when there’s a sudden supply shortage.What are the impacts? The number of participants in the sector will likely drop further, but largely from the fundamental side, as there’s still a good number of systematic commodity traders who aren’t concerned with supply and demand but only with the market’s technical aspects. This will keep volatility low and reduce liquidity in some of the smaller markets. But this is a structural trend that feasibly could reverse over time. The drop in the number of market makers will result in inefficient markets, more volatility and thus, more opportunity. And the reversal could come about faster should President Donald Trump succeed in jettisoning Dodd-Frank regulations.

This column does not necessarily reflect the opinion of the editorial board or Bloomberg LP and its owners.

Shelley Goldberg is an investment adviser and environmental sustainability consultant. She has worked as a commodities strategist for Brevan Howard Asset Management and Roubini Global Economics.