WASHINGTON — All those speculators getting the blame for driving up the price of oil these days — just who are they? For part of the answer, look in the mirror.

The retirement savings of workers across the country, entrusted to pension fund managers, are being plowed into one of the few investments that has delivered phenomenal returns in recent years.

For decades, futures contracts were mostly traded by commodity producers and the people who use the actual products, such as crude oil, corn and soybeans. Agreeing to a price today for a commodity to be delivered in, say, two months is a way to smooth out price fluctuations for those supplies.

But large investors faced with inflation have increasingly used them as protection against the falling dollar. That includes pension funds, along with investment banks, mutual funds and private hedge funds.

Research firm Ennis Knupp and Associates says $139 billion had been funneled into energy commodities, primarily crude oil, by the end of March — and it estimates that more than half of that is from retirement money.

The investments have paid off. The Standard & Poor's GSCI index, which tracks a basket of commodities, is up 19 percent in the past five years, compared with just 9 percent for the S&P 500 stock index.

The risk is that if the remarkable run in oil and other futures markets reverses course, billions of dollars of retirement benefits could be wiped out.

"A pension fund is supposed to be investing money in secure, stable investments for the benefit of the people whose money they are investing," said Dan Lippe, an energy analyst at Houston-based Petral Consulting Inc.

"When we hit that wall and things start falling," he said, "they will fall very fast, and the pension funds that invested in commodities will see a tremendous loss of value."

The retirement system for public employees in California, the nation's largest, has $1.3 billion invested in commodities.

That's still just 0.5 percent of the fund's total $240 billion in assets, said Michael Schlachter, who advises the fund. He said a collapse in oil or other commodity prices would have little effect on retirees.

Still, a growing chorus of experts is convinced retirement investments are enough to distort prices.

Billionaire George Soros, the airline industry and the International Monetary Fund are all pressuring Congress to curb speculation by large investors, and action may come by August.

"Your pension fund manager may be using your retirement money to drive up the price of oil," said Rep. Bart Stupak, D-Mich., at a hearing this week.

"What would happen if pension fund managers decided to increase their commodity investment by another 20-fold?"

In 2002, when the stock market swooned after the dot-com crash and 9/11, retirement assets dropped $7 billion, losing 8 percent of their value.

Speculators put money into commodity markets simply to make money on investments — unlike commercial investors, who are actually buying or selling orders for physical goods.

Energy analysts say it's unclear what effect speculators have had on oil prices, which climbed briefly to a new record above $142 yesterday before easing.

But Stupak and other lawmakers already have more than a dozen proposals to rein in commodity trading, including limiting how many contracts speculators can hold.

Schlachter, who is also managing director for investment consulting firm Wilshire Associates, said pension funds should not be compared to Wall Street speculators, who take huge risks every day to maximize returns.

"The pension plans we work with are using commodities only as a long-term hedge against inflation," he said.

Unlike the stock market, where there are a limited number of shares of each company, futures markets have no limits on contracts available. As long as a buyer can find a seller for each contract, investment opportunities are virtually unlimited.

Critics say retirement funds that accumulate contracts are artificially driving up commodity prices.

In the case of oil, that means higher prices for gas, food and other goods.

"If they're going to be in the futures market, they need to trade rather than take this buy and hold strategy," said Michael Masters, portfolio manager of hedge fund Masters Capital Management. "That is the worst possible thing for the futures market."