Don't sell yourself short, though, because for many people, achieving millionairehood -- and locking in long-term financial security through the end of retirement -- is much more possible than they thought. Check out the table below, based on data from University of Pennsylvania professor Jeremy Siegel, who studied returns of various investments over more than 200 years: That dividend growth can help you stay ahead of inflation, and when paired with stock-price appreciation over time, it makes for a nice one-two punch.