<prompt> Human: I dont dispute the advantages of Index funds as I am invested in them myself. The idea of instantmaximum diversification is excellent. However, I constantly read topics saying that you are basically guaranteed 5-7 returns year over year. With markets being at an all-time high how can this possibly be sustainable? I am all for the idea of compounding returns, but with index funds in particular you are betting on constantpermanent market expansion. Being new to investing I feel that due to market highs that I am guaranteed to take a significant hit ifwhen we hit a ceiling. I know this is not a predictable event, but the overall idea surrounding indexes just seems to good to be true. Curious for any thoughts on the subject. Note...not trying to get into the market doomsday scenario of everyone invested solely in indexes. Edit: Thanks for the replies. I was mistaken to refer to returns as guaranteed year over year. I meant to focus on the idea of a never-ending bull market long term.  <response>: Most literatures do not basically guaranteed 5-7 returns year over year. You are reading that incorrectly. Those are average returns. Some years the markets will be up 20-30, some years it will be down 20. Its just that the positive years have historically outweighed the negative years. 