Jack Bogle, Vanguard's founder, is on record stating that future returns in the financial markets will be below average. In his book and in recent interviews, Bogle has said expected returns for stocks and bonds should both be muted for the coming decade or so.
Based on current dividend, valuation and yield levels, Bogle predicts annual returns for U.S. stocks of about 4 percent, and of 3 percent for high quality U.S. bonds over the next 10 years. On a typical balanced 60/40 stock/bond portfolio, that would mean an annual return of just 3.6 percent. He admits that there are a host of factors that go into these types of forecasts so they are simply educated guesses.