<prompt> Human: Hi everyone,I would really appreciate your help in understanding index funds. Are the average annual returns of 24 from the vanguard site true? Nobody knows what will happen tomorrow, but most of the funds show 10 year average return to be in the 20-25 range.If I start out with 30K and make additional contributions of 20K a year for the next 10 years at 20-25, thats a mad future value. Do I sell the shares back to vanguard or to someone else to realize the gains? Is this really how it works? If someone who understands this can please take a few minutes to explain this to me in simple terms Id be very happy. Thanks!  <response>: I dont know where you got an average annual return of 24; I dont think any brokerage company actually advertises such a thing.More accurately, last year was a phenomenal year for investments and the SP did gain 24, so if you look at one-year returns, last year is very good. Historically, a typical aggressive portfolio achieved high single-digit returns on average which includes good years such as 2013, as well as bad years, such as the 2008 recession years. Note that inflation should be factored in to compute the real return. 