Commodities traders who buy and sell as much as $5.67 trillionof raw materials a year say the benchmark prices for everythingfrom oil to iron ore to gasoline are wrong as often as 27 percentof the time.

In a Bloomberg News survey conducted during the past eightweeks, 85 traders and analysts said they have little confidence inthe assessed prices of crude, metals and iron ore. Regulators,including European Union Competition Commissioner Joaquin Almunia,may examine commodities markets, having already increasedinvestigations of manipulation of benchmarks for interest rates,derivatives, foreign exchange and oil.

Five years after the global credit crisis prompted moreregulation of banks, benchmark prices for hundreds of commoditiesare determined through surveys of anonymous traders who may have astake in the outcome of the assessments. Unlike stock prices,available in real time at regulated exchanges for all investors tosee, many raw materials that go into food, clothing and power arebought and sold in private.