Chinese stocks will decline by an additional 14 percent over the next three weeks as the market demonstrates a trading pattern that mirrors the U.S. crash in 1929, according to Tom DeMark.

The Shanghai Composite Index will sink to 3,200 after plunging 8.5 percent Monday to 3,725.56 in the worst selloff in eight years, DeMark, who predicted the gauge’s bottom in 2013, said on Monday. That would extend its decline since a June 12 peak to 38 percent. The index’s moves since March are tracking those of the Dow Jones Industrial Average in 1929 when the gauge lost as much as 48 percent, he said in a phone interview.

While the securities regulator denied speculation that policy makers are withdrawing their support, concern is mounting that the unprecedented intervention to prop up share prices may not be sustainable as the economy slows.

“The die has been cast,” said DeMark, 68, the founder of DeMark Analytics in Scottsdale, Arizona, who has spent more than 40 years developing indicators to identify market turning points. “You just cannot manipulate the market. Fundamentals dictate markets.”

Government Support

He made similar statements in February 2014 about the Standard & Poor’s 500 Index, saying that if certain conditions were met, U.S. stocks had reached a point resembling the time before the 1929 market crash. The S&P 500 rallied 8 percent over the next two months. He said Monday that those conditions didn’t materialize at the time.

The Shanghai gauge had rebounded 16 percent from its July 8 low through Friday as officials went to extreme lengths to support stocks. Officials allowed more than 1,400 companies to halt trading, suspended initial public offerings and supplied China Securities Finance Corp., a state-run financing vehicle with more than $480 billion to intervene in markets.

The benchmark index dropped 1.7 percent at the close on Tuesday.

China Securities Finance hasn’t pulled support for equities and the government will “continue efforts to stabilize market and investor sentiment,” China Securities Regulatory Commission spokesman Zhang Xiaojun said in a statement after the close of trading Monday.

DeMark said the intervention won’t be able to sustain the recent rally.