WASHINGTON – An independent U.S. study of oil markets concludes that speculation by large investors is the primary reason for the massive rise and fall in oil prices this year.

The study says investors poured $60 billion into oil futures markets in the first six months of the year as oil prices soared from $95 to $145 a barrel,

They have since withdrawn $39 billion from those same markets as prices have retreated.

Michael Masters of Masters Capital Management, which did the study, says the flow of money – not major changes in supply and demand – caused the volatile movement of oil prices.

The report was released Wednesday by U.S. Senate and House sponsors of bills to put additional curbs on oil market speculation.