Co-Chief Investment Officer and Co-Founder of PIMCO Bill Gross asserts that stock investing is “dead as we know it” in his August investment letter.

Pacific Investment Management Company has $1.82 trillion in assets is the world’s largest bond mutual fund.

“If financial assets no longer work for you at a rate far and above the rate of true wealth creation, then you must work longer for your money,” Gross wrote.

Gross took particular issue with the Siegel constant of 6.6 percent return from stocks, calling the past percentage return “[a] historical freak, a mutation likely never to be seen again as far as we mortals are concerned.”

Earlier this month Gross predicted real GDP growth at 1.5 percent for the next decade. Based on this assumption, investors should get used to smaller investment returns.