Paul Singer’s Elliott Management Corp. said optimism on U.S. growth is misguided as economic data understate inflation and overstate growth, and central bank policies of the past six years aren’t sustainable.

The market turmoil in the first half of October may be a “coming attractions” for the next real crash that could turn into a “deep financial crisis” if investors lose confidence in the effectiveness of monetary stimulus, Elliott wrote in a third-quarter letter to investors, a copy of which was obtained by Bloomberg News. Elliott also said an “incompetent global response” to the Ebola epidemic may be a precursor to a “severe” global economic slump.

“Nobody can predict how long governments can get away with fake growth, fake money, fake jobs, fake financial stability, fake inflation numbers and fake income growth,” New York-based Elliott wrote. “When confidence is lost, that loss can be severe, sudden and simultaneous across a number of markets and sectors.”

The 70-year-old Singer, one of the biggest backers of Republican politicians, reiterated criticisms of the Federal Reserve and central banks globally for quantitative easing. Reported growth numbers are too high because the official inflation number is “simply too low” as economists accept “adjustments and tricks” that are part of understating and distorting the measure, Elliott wrote.

While the U.S. is doing better than the rest of the world, the acceleration in the second quarter only reversed a “terrible” first quarter and has yet to be sustained in the remainder of the year, Elliott wrote.

“We do not think this optimism is warranted, and we think a lot of the data is cooked or misleading,” Elliott wrote. “A good deal of the economic and jobs growth since the crisis has been fake growth, with very little chance of being self-reinforcing and sustainable.”

Singer founded the $25.4 billion investment firm in 1977. Its oldest fund has delivered compounded annual returns of 13.9 percent since inception.