You are replying with a fixed period that confirms your claim while comment OP was talking about total returns which you can be sure are not zero. If you are handpicking periods you can find a month in the last 2 years that was negative and make a claim that the stock market didn't go up but it did, > 100%.
Real Total return (inflation adjusted, dividends included) of SP500 has been negative in two decades. 1970s and 2000s.
The original claim is 10-20 years. That's a valid ballpark estimate. There can be lost decades, but when you get closer to 20 years, it has been all good.
ps. If you spread the entry into market into 5-10 years there has never been a decade of zero or negative returns (total, inflation adjusted).
