Blaming speculators for the rapid rise in oil and food costs has become a bipartisan sport in Washington. This may succeed in building public outrage at supposedly wealthy investors (while diverting attention from lawmakers’ failure to take meaningful action on energy), but that anger may be misplaced, or at least overblown.

“The increased cost of energy certainly reflects fundamentals, including increased demand from China and India, but institutional investors also appear to be driving up prices. Increased regulation and transparency in the futures markets is needed to guard against excessive speculation and price manipulation,” Sen. Susan Collins said after the Senate Homeland Security and Governmental Affairs recently held its second hearing on speculation.

In Bangor earlier this month, Rep. Tom Allen, who is challenging Sen. Collins in this fall’s election, also took aim at speculators. “I will continue my work to crack down on speculation, which is driving up the cost of oil by as much as $1 per gallon. Speculators must be held accountable for reaping excess profits on the backs of hard-working Mainers,” he added.

Sen. Olympia Snowe and Rep. Mike Michaud also have condemned speculators in recent statements.

Not so fast, says Newsweek columnist Robert Samuelson. He offers a compelling counterargument in the magazine’s July 14 issue.

Yes, the price of oil and corn have risen dramatically since 2002, he writes. But so has the price of steel and iron, neither of which are traded on commodities markets. Rio Tinto, a large mining company, recently disclosed that prices for iron ore destined to Chinese customers rose an average of 85 percent. “That was stunning proof that physical supply and demand – not financial shenanigans – are setting prices.”

In another example, Mr. Samuelson notes that world wheat stocks are near historic lows.

The rising demand for many commodities is driven by growth of the economies in China and India. “In industry after industry, global buying has bumped up against production limits,” Mr. Samuelson writes. The result: higher prices.

And who buys commodities futures contracts, basically a bet on whether prices for certain raw materials will rise or fall? In large part, pension funds, university endowments and foundations, seeking higher returns.

While more transparency in commodities markets is overdue, it is unlikely to dramatically decrease prices.