AP

BASHING “speculators” is a popular pastime for American politicians trying to explain high and volatile oil prices. But whether speculation has really been responsible for spiking prices is a controversial issue. In 2008 the Commodity Futures Trading Commission (CFTC) issued a report dismissing the role of speculators in last year's startling run-up in prices. But banks, hedge funds and others who bet on oil (without a use for the stuff itself) still face limits on the positions they can take, if Gary Gensler, the new CFTC head, can show that their influence in markets does harm.

On September 4th the CFTC added more evidence to the debate by releasing what it said were more transparent data on market positions. Before this month, the CFTC simply classified traders as “commercial” or “non-commercial” in its weekly report on the overall long and short positions in the market. Now it has started to disaggregate them further, into producers and buyers, swap dealers and “managed money”. The third category includes hedge funds.

What do the new data show? On the New York Mercantile Exchange (NYMEX) swap dealers and managed money were both long on oil in the week to September 1st—the former by more than a 2-to-1 ratio. Producers and users, by contrast, are net short on oil by similar margins. And the swap dealers and managed-money players are bigger in the market, both in terms of the contracts they hold and their own sheer numbers.

But analysts at Barclays Capital note that long swaps accounted for just 6.4% of total futures and options contracts, not enough to drive prices up on their own. Physical traders held more of the outstanding long positions (10.3%) and held even more short positions. This one set of numbers, in other words, does little to prove that speculators are overriding market fundamentals to drive prices. New quarterly data also released by the CFTC show that money flows to exchange-traded funds (ETFs) in commodities failed to correlate strongly with last year's price surge.

There are more disclosures to come. The CFTC says it will soon release the newly disaggregated data going back three years. If those numbers, like the quarterly ETF data, are equally unconvincing on the role of speculation, the case for limiting positions will be weakened. And a strong counter-argument remains: that speculators provide crucial liquidity. Even if they also have some effect on prices, taking them out of the game could well do more harm than good. It is tempting to look for scapegoats when high prices hurt consumers. But the real culprits for oil-price volatility may be much more familiar: supply, demand and global instability.