Passive commodity investors scaled back bullish bets on US crude oil while it surged last year, then boosted them as it declined, statistics released on Friday showed.

The figures update a controversial government report issued a year ago, and reinforce its assertion that flows of money tracking commodity indexes correlated poorly with oil prices. In December 2007, when West Texas Intermediate crude was $96 a barrel, index investors were net buyers of futures equal to 413m barrels, the Commodity Futures Trading Commission said. By June 2008 the net bullish position had declined to 366m barrels equivalent, while crude hit $140.