The stock market? "Appears to show" - FIFY. I'm reminded of the periodic 401(k) presentations at our company before I retired; the pitchperson would always put up the same, tired, old, vague graph of the stock market rising at a 45-degree angle from the Great Depression to the present time. But that's not really true, is it? Indexes like the DJIA are mathematical models that get reformulated periodically and the suite of companies included in an index also changes over time. I believe this is called cherry-picking the data.
Actual investors in individual stocks or mutual funds have no guarantee of generational growth, of course. In NYT's Justin Fox's book about the stock market, IIRC, he said that equity mutual funds had an annual average growth rate a little above 2% between 1984 and the early 2000s, while the S&P 500's annual growth rate averaged about 12%. (Dates and growth rates are approximate as I don't have the book at hand). 401(k)ers didn't exactly make out like bandits.