Is a “total stock market” index fund diverse enough alone?
You're missing the concept of systemic risk, which is the risk of the entire market or an entire asset class. Diversification is about achieving a balance between risk and return that's appropriate for you. Your investment in Vanguard's fund, although diversified between many public companies, is still restricted to one asset class in one country. Yes, you lower your risk by investing in all of these companies, but you don't erase it entirely.  Clearly, there is still risk, despite your diversification. You may decide that you want other investments or a different asset allocation that reduce the overall risk of your portfolio. Over the long run, you may earn a high level of return, but never forget that there is still risk involved. bonds seem pretty worthless, at least until I retire According to your profile, you're about my age. Our cohort will probably begin retiring sometime around 2050 or later, and no one knows what the bond market will look like over the next 40 years. We may have forecasts for the next few years, but not for almost four decades. Writing off an entire asset class for almost four decades doesn't seem like a good idea. Also, bonds are like equity, and all other asset classes, in that there are different levels of risk within the asset class too. When calculating the overall risk/return profile of my portfolio, I certainly don't consider Treasuries as the same risk level as corporate bonds or high-yield (or junk) bonds from abroad.  Depending on your risk preferences, you may find that an asset allocation that includes US and/or international bonds/fixed-income, international equities, real-estate, and cash (to make rebalancing your asset allocation easier) reduces your risk to levels you're willing to tolerate, while still allowing you to achieve returns during periods where one asset class, e.g. equities, is losing value or performing below your expectations. and seems to do better than the S&P 500 too. No, that's not true. In fact, this fund is somewhere between S&P500 and the NASDAQ Composite indexes wrt to performance. From my experience (I have it too), it seems to fall almost in the middle between SPY and QQQ in daily moves. So it does provide diversification, but you're basically diversifying between various indexes. The cost is the higher expense ratios (compare VTI to VOO). Write off the entire asset class of corporate bonds? Finance theory says yes, the only two asset classes that you need are stocks and treasury bills (very short-term US government bonds). See the Capital Asset Pricing Model (CAPM). I don't think you are missing much, if anything, Brendan. You get massive diversification and low fees with a fund like VTI. I'm not sure if it is good to have everything with only one broker though. I would add to the conversation that the goal shouldn't be to have a giant pile of money in x years..and then spend it down in retirement. A much better/safer goal is to have enough dividends being generated that you never have to touch your capital. Looks like you are starting young so congrats. "Brendan, The short answer is no, there is no need to get into any other funds. For all intents and purposes the S&P 500 is ""The Stock Market"". The news media may quote the Dow when the market reaches new highs or crashes but all of the Dow 30 stocks are included in the S&P 500.  The S&P is also marketcap weighted, which means that it owns in higher proportion the big ""Blue Chip"" stocks more than the smaller less known companies. To explain, the top 10 holdings in the S&P represent 18% of the total index, while the bottom 10 only represent 0.17% (less than 1 percent). They do have an equal weighted S&P in which all 500 companies represent only 1/500th of the index and that is technically even more diversified but in actuality it makes it more volatile because it has a higher concentration of those smaller less known companies. So it will tend to perform better during up markets and worse during down markets. As far as diversification into different asset classes or other countries, that's non-sense. The S&P 500 has companies in it that give you that exposure. For example, it includes companies that directly benefit from rising oil prices, rising gold prices, etc known as the Energy and Materials sector. It also includes companies that own malls, apartment complexes, etc. known as the Real Estate sector. And as far as other countries, most of the companies in the S&P are multi-national companies, meaning that they do business over seas in many parts of the world. Apple and FaceBook for example sell their products in many different countries. So you don't need to invest any of your money into an Emerging Market fund or an Asia Fund because most of our companies are already doing business in those parts of the world. Likewise, you don't need to specifically invest into a real estate or gold fund.  As far as bonds go, if you're in your twenties you have no need for them either. Why, because the S&P 500 also pays you dividends and these dividends grow over time. So for example, if Microsoft increases its dividend payment by 100% over a ten year period , all of the shares you buy today at a 2.5% yield will, in 10 years, have a higher 5% yield. A bond on the other hand will never increase its yield over time. If it pays out 4%, that's all it will ever pay. You want to invest because you want to grow your money and if you want to invest passively the fastest way to do that is through index ETFs like the $SPY, $IVV, and $RSP. Also look into the $XIV, it's an inverse VIX ETF, it moves 5x faster than the S&P in the same direction. If you want to actively trade your money, you can grow it even faster by getting into things like options, highly volatile penny stocks, shorting stocks, and futures. Don't get involved in FX or currency trading, unless it through futures." Good idea to stay only with VTI if you are 30. For 50, I recommend: 65% VTI 15% VOO 10% VXUS 10% BND
"Typically you diversify a portfolio to reduce risk. The S&P 500 is a collection of large-cap stocks; a diversified portfolio today probably contains a mix of large cap, small cap, bonds,  international equity and cash. Right now, if you have a bond component, that part of your portfolio isn't performing as well. The idea of diversification is that you ""smooth out"" the ups and downs of the market and come out ahead in most situations. If you don't have a bond or cash component in your portfolio, you may have picked (or had someone pick for you) lousy funds.  Without more detail, that's about all that can be said. EDIT: You provided more detail, so I want to add a little to my answer. Basically, you're in a fund that has high fees (1.58% annually) and performance that trails the mid-cap index. The S&P 500 is a large-cap index (large cap == large company), so a direct comparison is not necessarily meaningful. Since you seem to be new at this, I'd recommend starting out with the Vanguard Total Stock Market Index Fund (VTSMX) or ETF (VTI). This is a nice option because it represents the entire stock market and is cheap... it's a good way to get started without knowing alot. If your broker charges a transaction fee to purchase Vanguard funds and you don't want to change brokers or pay ETF commissions, look for or ask about transaction-fee free ""broad market"" indexes. The expense ratio should be below 0.50% per year and optimally under 0.20%. If you're not having luck finding investment options, swtich to a discount broker like TD Ameritrade, Schwab, ScottTrade or Fidelity (in no particular order)" As a corollary to this; the average investor will never know more than the market. Buffett can buy mispriced securities because he runs a multi-billion dollar company dedicated to finding these mispricings.   My advice for the common man:  1. Invest in both Stocks (for growth) &amp; Bonds (for wealth preservation) 2. Stocks should be almost exclusively Index Funds  That's it.  The stock market has a 'random walk with a positive drift' which means that in general, the market will increase in value. Index funds capture this value and will protect you against the inevitable BoA, AIG, Enron, etc.   It's fine to invest in index funds with a strategy as well, for instance emerging market ETFs could capture the growth of a particular region. Bear ETFs are attractive if you think the market is going to hit a downturn in the future. "when the index is altered to include new players/exclude old ones, the fund also adjusts The largest and (I would say) most important index funds are whole-market funds, like ""all-world-ex-US"", or VT ""Total World Stock"", or ""All Japan"".  (And similarly for bonds, REITS, etc.)  So companies don't leave or enter these indexes very often, and when they do (by an initial offering or bankruptcy) it is often at a pretty small value. Some older indices like the DJIA are a bit more arbitrary but these are generally not things that index funds would try to match. More narrow sector or country indices can have more of this effect, and I believe some investors have made a living from index arbitrage.  However well run index funds don't need to just blindly play along with this. You need to remember that an index fund doesn't need to hold precisely every company in the index, they just need to sample such that they will perform very similarly to the index.  The 500th-largest company in the S&P 500 is not likely to have all that much of an effect on the overall performance of the index, and it's likely to be fairly correlated to other companies in similar sectors, which are also covered by the index.  So if there is a bit of churn around the bottom of the index, it doesn't necessarily mean the fund needs to be buying and selling on each transition.  If I recall correctly it's been shown that holding about 250 stocks gives you a very good match with the entire US stock market." One thing to be aware of when choosing mutual funds and index ETFs is the total fees and costs. The TD Ameritrade site almost certainly had links that would let you see the total fees (as an annual percentage) for each of the funds. Within a category, the lowest fees percentage is best, since that is directly subtracted from your performance. As an aside, your allocation seems overly conservative to me for someone that is 25 years old. You will likely work for 40 or so years and the average stock market cycle is about 7 years. So you will likely see 5 or so complete cycles. Worrying about stability of principal too young will really cut into your returns. My daughter is your age and I have advised her to be 100% in equities and then to start dialing that back in about 25 years or so. One thing to be aware of when choosing mutual funds and index ETFs is the total fees and costs. The TD Ameritrade site almost certainly had links that would let you see the total fees (as an annual percentage) for each of the funds. Within a category, the lowest fees percentage is best, since that is directly subtracted from your performance. As an aside, your allocation seems overly conservative to me for someone that is 25 years old. You will likely work for 40 or so years and the average stock market cycle is about 7 years. So you will likely see 5 or so complete cycles. Worrying about stability of principal too young will really cut into your returns. My daughter is your age and I have advised her to be 100% in equities and then to start dialing that back in about 25 years or so. This is the chart going back to the first full year of this fund.  To answer your question - yes, a low cost ETF or Mutual fund is fine. Why not go right to an S&P index? VOO has a .05% expense. Why attracted you to a choice that lagged the S&P by $18,000 over this 21 year period?  (And yes, past performance, yada, yada, but that warning is appropriate for the opposite example. When you show a fund that beat the S&P short term, say 5 years, its run may be over. But this fund lagged the S&P by a significant margin over 2 decades, what makes you think this will change? Let's simplify things by assuming you only own 2 stocks. By owning VOO and VTI, you're overweight on large- and mid-cap stocks relative to the market composition. Likewise, by owning VTI and VT, you're overweight on U.S. stocks; conversely, by owning VXUS and VT, you're overweight on non-U.S. stocks. These are all perfectly fine positions to take if that's what you intend and have justification for. For example, if you're in the U.S., it may be a good idea to hold more U.S. stocks than VT because of currency risk. But 4 equity index ETFs is probably overcomplicating things. It is perfectly fine to hold only VTI and VXUS because these funds comprise thousands of stocks and thus give you sufficient diversification. I would recommend holding those 2 ETFs based on a domestic/international allocation that makes sense to you (Vanguard recommends 40% of your stock allocation to be international), and if for some reason you want to be overweight in large- and mid-cap companies, throw in VOO. You can use Morningstar X-Ray to look at your proposed portfolio and find your optimal mix of geographic and stock style allocation. For index funds to be a poor investment, they would have to perform worse than your alternative investments.  In this case, we'll assume the alternative to be the individual stocks.  Obviously, it must be possible to pick just the winning stocks and avoid the losing stocks, raising your rate of return... however, several studies have shown that individuals are horrible at picking winners.  We let our emotions, are biases, and are suppositions get in the way.  You could literally throw a dart, but then you either win big or lose big.  Picking the fund evens that out for you, so you don't win or lose big, but just get a consistently boring (yet consistently good) return. If you have a lot of time to put into the research, and are confident in your ability to pick winning stocks, then you can do better than the index funds.  Otherwise, sticking with the index fund is probably a smart choice.