Why would I want a diversified portfolio, versus throwing my investments into an index fund?
"Index funds are well-known to give the best long-term investment. Not exactly. Indexes give the best long term performance when compared to actively managing investments directly in the underlying stocks. That is, if you compare an S&P500 index to trying to pick stocks that are part of it, you're more likely to succeed with blindly following the index than trying to actively beat it. That said, no-one promises that investing in S&P500 is better than investing in DJIA, for example. These are two different indexes tracking different stocks and areas. So when advisers say ""diversify"" they don't mean it that you should diversify between different stocks that build up the S&P500 index. They mean that you should diversify your investments in different areas. Some in S&P500, some in DJIA, some in international indexes, some in bond indexes, etc. Still, investing in various indexes will likely yield better results than actively managing the investments trying to beat those indexes, but you should not invest in only one, and that is the meaning of diversification. In the comments you asked ""why diversify at all?"", and that is entirely a different question from your original ""what diversification is?"". You diversify to reduce the risk of loss from one side, and widen the net for gains from another. The thing is that any single investment can eventually fail, regardless of how it performed before. You can see that the S&P500 index lost 50% of its value twice within ten years, whereas before it was doubling itself every several years. Many people who were only invested in that index (or what's underlying to it) lost a lot of money. But consider you've diversified, and in the last 20 years you've invested in a blend of indexes that include the S&P500, but also other investments like S&P BSE SENSEX mentioned by Victor below. You would reduce your risk of loss on the American market by increasing your gains on the Indian market. Add to the mix soaring Chinese Real Estate market during the time of the collapse of the US real-estate, gains on the dollar losing its value by investing in other currencies (Canadian dollar, for example), etc. There are many risks, and by diversifying you mitigate them, and also have a chance to create other potential gains. Now, another question is why invest in indexes. That has been answered before on this site. It is my opinion that some methods of investing are just gambling by trying to catch the wave and they will almost always fail, and rarely will individual stock picking beat the market. Of course, after the fact its easy to be smart and pick the winning stocks. But the problem is to be able to predict those charts ahead of time." "Diversification is extremely important and the one true ""Free Lunch"" of investing, meaning it can provide both greater returns and less risk than a portfolio that is not diversified. The reason people say otherwise is because they are talking about ""true"" portfolio diversification, which cannot be achieved by simply spreading money across stocks. To truly diversify a portfolio it must be diversified across multiple, unrelated ""Return Drivers."" I describe this throughout my best-selling book and am pleased to provide complimentary links to the following two chapters, where I discuss the lack of diversification from spreading money solely across stocks (including correlation tables), as well as the benefits of true portfolio diversification: Jackass Investing - Myth #8: Trading is Gambling – Investing is Safer Jackass Investing - Myth #20: There is No Free Lunch" Index funds are well-known to give the best long-term investment. Are they? Maybe not all the time! If you had invested in an index fund tracking the S&P500 at the start of 2000 you would still be behind in terms of capital appreciation when taking inflation into considerations. Your only returns in 13.5 years would have been any dividends you may have received. See the monthly chart of the S&P500 below.  Diversification can be good for your overall returns, but diversification simply for diversification sake is as you said, a way of reducing your overall returns in order of smoothing out your equity curve. After looking up indexes for various countries the only one that had made decent returns over a 13.5 year period was the Indian BSE 30 index, almost 400% over 13.5 years, although it also has gone nowhere since the end of 2007 (5.5 years). See monthly chart below.  So investing internationally (especially in developing countries when developed nations are stagnating) can improve your returns, but I would learn about the various international markets first before plunging straight in. Regarding investing in an Index fund vs direct investment in a select group of shares, I did a search on the US markets with the following criteria on the 3rd January 2000:  If the resulting top 10 from the search were bought on 3rd January 2000 and held up until the close of the market on the 19th June 2013, the results would be as per the table below:  The result, almost 250% return in 13.5 years compared to almost no return if you had invested into the whole S&P 500 Index. Note, this table lists only the top ten from the search without screening through the charts, and no risk management was applied (if risk management was applied the 4 losses of 40%+ would have been limited to a maximum of 20%, but possibly much smaller losses or even for gains, as they might have gone into positive territory before coming back down - as I have not looked at any of the charts I cannot confirm this). This is one simple example how selecting good shares can result in much better returns than investing into a whole Index, as you are not pulled down by the bad stocks.
Is there a reason you are focusing on stocks? A portfolio of $4,000 in stocks alone will not give you much diversification, and buying $40 of 100 stocks will not have enough impact to grow your portfolio in the way it sounds like you would like it to.  Have you considered using ETFs? The reason diversification in general is a benefit is easily seen in your first graph.  While the purple line (Betterment 100% Stock) is always below the blue line (S&P), and the blue line is the superior return over the entire period, it's a bit different if you retired in 2009, isn't it?  In that case the orange line is superior: because its risk is much lower, so it didn't drop much during the major crash.  Lowering risk (and lowering return) is a benefit the closer you get to retirement as you won't see as big a cumulative return from the large percentage, but you could see a big temporary drop, and need your income to be relatively stable (if you're living off it or soon going to).   Now, you can certainly invest on your own in a diverse way, and if you're reasonably smart about it and have enough funds to avoid any fees, you can almost certainly do better than a managed solution - even a relatively lightly managed solution like Betterment.  They take .15% off the top, so if you just did exactly the same as them, you would end up .15% (per year) better off. However, not everyone is reasonably smart, and not everyone has much in the way of funds. Betterment's target audience are people who aren't terribly smart about investing and/or have very small amounts of funds to invest.  Plenty of people aren't able to work out how to do diversification on their own; while they probably mostly aren't asking questions on this site, they're a large percentage of the population.  It's also work to diversify your portfolio: you have to make minor changes every year at a minimum to ensure you have a nicely balanced portfolio.  This is why target retirement date portfolios are very popular; a bit higher cost (similar to Betterment, roughly) but no work required to diversify correctly and maintain that diversification. Picking yourself is just what all the fund managers are trying to do, and history shows that the majority of them fails the majority of the time to beat the index fund. That is the core reason of the current run after index funds. What that means is that although it doesn’t sound so hard, it is not easy at all to beat an index consistently. Of course you can assume that you are better than all those high-paid specialists, but I would have some doubt. You might be luckier, but then you might be not. Lots of good answers.  I'll try and improve by being more brief.  For each option you will pay different taxes: Index Fund:   Traditional IRA Roth IRA You can see that the Roth IRA is obviously better than investing in a taxable account.  It may not be as obvious that the traditional IRA is better as well.  The reason is that in the traditional account you can earn returns on the money that otherwise would have gone to the government today.  The government taxes that money at the end, but they don't take all of it. In fact, for a given investment amount X and returns R, the decision of Roth vs Traditional depends only on your tax rate now vs at retirement because X(1-tax)(1+R_1)(1+R_2)...(1+R_n) = X(1+R_1)(1+R_2)...(1+R_n)(1-tax) The left hand side is what you will have at retirement if you do a Roth and the right hand side is what you will have at retirement if you do traditional.  Only the tax rate differences between now and retirment matter here.  An index fund investment is like the left hand side but has some additional tax terms on your capital gains.  It's clearly worse than either. I think you need a diversified portfolio, and index funds can be a part of that. Make sure that you understand the composition of your funds and that they are in fact invested in different investments. 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). No, there is no real advantage. The discrepancies in how they track the index will (generally) be so small that this provides very, very limited diversification, while increasing the complexity of your investments. Why would it not make more sense to invest in a handful of these   heavyweights instead of also having to carry the weight of the other   450 (some of which are mostly just baggage)? First, a cap-weighted index fund will invest more heavily in larger cap companies, so the 'baggage' you speak of does take up a smaller percentage of the portfolio's value (not that cap always equates to better performance). There are also equal-weighted index funds where each company in the index is given equal weight in the portfolio. If you could accurately pick winners and losers, then of course you could beat index funds, but on average they've performed well enough that there's little incentive for the average investor to look elsewhere.  A handful of stocks opens you up to more risk, an Enron in your handful would be pretty devastating if it comprised a large percentage of your portfolio. Additionally, since you pay a fee on each transaction ($5 in your example), you have to out-perform a low-fee index fund significantly, or be investing a very large amount of money to come out ahead. You get diversification and low-fees with an index fund. "Here is my simplified take: In any given market portfolio the market index will return the average return on investment for the given market. An actively managed product may outperform the market (great!), achieve average market performance (ok - but then it is more expensive than the index product) or be worse than the market (bad).  Now if we divide all market returns into two buckets: returns from active investment and returns from passive investments then these two buckets must be the same as index return are by definition the average returns. Which means that all active investments must return the average market return.  This means for individual active investments there are worse than market returns and better then market returns - depending on your product. And since we can't anticipate the future and nobody would willingly take the ""worse than market"" investment product, the index fund comes always up on top - IF - you would like to avoid the ""gamble"" of underperforming the market. With all these basics out of the way: if you can replicate the index by simply buying your own stocks at low/no costs I don't see any reason for going with the index product beyond the convenience." "Beatrice does a good job of summarizing things.  Tracking the index yourself is expensive (transaction costs) and tedious (number of transactions, keeping up with the changes, etc.)  One of the points of using an index fund is to reduce your workload.  Diversification is another point, though that depends on the indexes that you decide to use.  That said, even with a relatively narrow index you diversify in that segment of the market. A point I'd like to add is that the management which occurs for an index fund is not exactly ""active.""  The decisions on which stocks to select are already made by the maintainers of the index.  Thus, the only management that has to occur involves the trades required to mimic the index." If you are diversifying just for diversification purposes then all you are doing is averaging down your returns. You shouldn't just buy two securities because you think it is safer than putting all your money into one. A better method is to use money management and position sizing to limit your risk and exposure in any one security. You should know what your maximum risk is before you buy any security and know when it is time to get out of it. There are better ways to manage your risk. Don't put all your eggs in the one basket - yes, but don't diversify just for diversification purposes. When you are starting out using a balanced fund can be quite advantageous. A balanced fund is represents a diversified portfolio in single fund. The primary advantage of using a balanced fund is that with it being a single fund it is easier to meet the initial investment minimum.  Later once you have enough to transition to a portfolio of diversified funds you would sell the fund and buy the portfolio. With a custom portfolio, you will be better able to target your risk level and you might also be able to use lower cost funds.  The other item to check is do any of the funds that you might be interested in for the diversified portfolio have lower initial investment option if you can commit to adding money on a specified basis (assuming that you are able to). Also there might be an ETF version of a mutual fund and for those the initial investment amount is just the share price. The one thing to be aware of is make sure that you can buy enough shares that you can rebalance (holding a single share makes it hard to sell some gain when rebalancing). I would stay away from individual stocks until you have a much larger portfolio, assuming that you want to invest with a diversified portfolio. The reason being that it takes a lot more money to create a diversified portfolio out of individual stocks since you have to buy whole shares. With a mutual fund or ETF, your underlying ownership of can be fractional with no issue as each fund share is going to map into a fraction of the various companies held and with mutual funds you can buy fractional shares of the fund itself. Is it POSSIBLE? Of course. I don't even need to do any research to prove that. Just some mathematical reasoning: Take the S&P 500. Find the performance of each stock in that list over whatever time period you want to use for your experiment. Now select some number of the best-performing stocks from the list -- any number less than 500. By definition, the X best must be better than or equal to the average. Assuming all the stocks on the S&P did not have EXACTLY the same performance, these 10 must be better than average. You now have a diversified portfolio that performed better than the S&P 500 index fund. Of course as they always say in a prospectus, past performance is not a guarantee of future performance.  It's certainly possible to do. The question is, if YOU selected the stocks making up a diversified portfolio, would your selections do better than an index fund? I choose lifecycle funds because I am placing faith (perhaps foolishly) that a full time fund manager knows better what to pick than I.  The same reason I go with mutual funds in general apply to to why I also have the lifecycle funds.  Presently my diversification strategy is really just index funds and lifecycle funds. The radio advice guy Clark Howard often promotes them. http://www.wacotrib.com/none/content/shared/money/stories/clark/0601/060425money.html (I count in the intimidated group) Lets imagine two scenarios: 1) You make 10.4k (40% of total income) yearly contributions to a savings account that earns 1% interest for 10 years. In this scenario, you put in 104k and earned 5.89k in interest, for a total of 109.9k. 2) You make the same 10.4k yearly contribution to an index fund that earns 7% on average for 10 years. In this scenario you put in the same 104k, but earned 49.7k in interest*, for a total of 153.7k. The main advantage is option 1) has more liquidity -- you can get the money out faster. Option 2) requires time to divest any stocks / bonds. So you need enough savings to get you through that divestment period. Imagine another two scenarios where you stop earning income: 1-b) You stop working and have only your 109.9k principal amount in a 1% savings account. If you withdraw 15.6k yearly for your current cost of living, you will run through your savings in 7 years. 2-b) You stop working and have only 20k (2 years of savings) in savings that earns 1% with 153.7k in stocks that earns 7%. If you withdraw your cost of living currently at 15.6k, you will run through your investments in 15 years and your savings in 2 years, for a total of 17 years. The two years of income in savings is extremely generous for how long it starts the divestment process.  In summary, invest your money. It wasn't specified what currency we are talking about, but you can easily find access to an investment company no matter where you are in the world. Keep a small amount for a rainy day.