PetroChina Co has about 11 billion barrels of oil reserves, half a million employees and sales that exceed the annual economic output of South Africa.

Not too long ago, stats like that were important to traders of PetroChina shares. Now, they could hardly matter less.

As State-linked funds intervene to prop up the nation's sinking stocks, PetroChina has transformed into a speculative bet on how much money the government is plowing into equities on any given day. The $310 billion oil producer's top weighting in the benchmark Shanghai Composite Index makes it an ideal target for funds trying to influence the broader market.

The result has been a surge in PetroChina's volatility to the highest level among the world's 100 biggest companies - fluctuations so big that they top 95 percent of the stocks in America's small-cap Russell 2000 Index. The swings are another sign of how State intervention is leading to price distortions in the world's second-largest equity market.

"This market is not a stock market that's driven by fundamentals," Donald Straszheim, the head of China research at New York-based Evercore ISI, said in a July 30 interview. "It is a government operation. Beijing is calling the tune, day by day."

A gauge of 30-day price swings in PetroChina's Shanghai-listed shares jumped to the highest since December 2007 last week. The stock moved at least 4 percent on half the trading days in July, including a record 9.6 percent plunge on July 27.

The oil company's shares fell 4.7 percent at the close on Monday, while the Shanghai Composite Index dropped 1.1 percent.

At 82, PetroChina's level of volatility is so high that the most comparable stock in the US is Gastar Exploration Inc, an energy company with a market value of just $134 million.

It's not just PetroChina getting whiplashed. The five most volatile stocks among the 100 largest members of the Bloomberg World Index are all Chinese. They include China Life Insurance Co, Bank of China Ltd and China Petroleum & Chemical Corp. Price swings on the Shanghai Composite climbed to the highest level since 1997 last week.

"Government support induces speculation," said Ronald Wan, the chief executive at Partners Capital International in Hong Kong.

A lack of transparency from authorities about their support measures is also fueling volatility. After a government rescue package helped drive a 16 percent rebound in the Shanghai Composite Index from its July 8 low, that support appeared to vanish without warning last Monday, when the gauge plunged 8.5 percent. The rout left analysts to guess whether officials shifted their policy stance or were just overwhelmed by a flood of sell orders.