What does a well diversified self-managed investment portfolio look like?
Diversified is relative. Alfred has all his money in Apple.  He's done very well over the last 10 years, but I think most investors would say that he's taking an incredible risk by putting everything on one stock. Betty has stock in Apple, Microsoft, and Google.  Compared to Alfred, she is diversified. Charlie looks at Betty and realizes that she is only investing in one particular industry.  All the companies in an individual industry can have a downturn together, so he invests everything in an S&P 500 index fund. David looks at Charlie and notes that he's got everything in large, high-capitalization companies.  Small-cap stocks are often where the growth happens, so he invests in a total stock market fund. Evelyn realizes that David has all his money tied up in one country, the United States.  What about the rest of the world?  She invests in a global fund. Frank really likes Evelyn's broad approach to equities, but he knows that some portion of fixed-income assets (e.g. cash deposits, bonds) can reduce portfolio volatility—and may even enhance returns through periodic rebalancing. He does what Evelyn does, but also allocates some percentage of his portfolio to fixed income, and intends to maintain his target allocations. Being diversified enough depends on your individual goals and investing philosophy.  There are some who would say that it is wrong to put all of your money in one fund, no matter what it is.  Others would say that a sufficiently broad index fund is inherently diversified as-is. "When you invest in a single index/security, you are completely exposed to the risk of that security. Diversification means spreading the investments so the losses on one side can be compensated by the gains on the other side. What you are talking about is one thing called ""risk apettite"", more formally known as Risk Tolerance: Risk tolerance is the degree of variability in investment returns that an investor is willing to withstand. (emphasis added) This means that you are willing to accept some losses in order to get a potential bigger return. Fidelity has this graph:  As you can see in the table above, the higher the risk tolerance, the bigger the difference between the best and worst values. That is the variability. The right-most pie can be one example of an agressive diversified portfolio. But this does not mean you should go and buy exactly that security compostion. High-risk means playing with fire. Unless you are a professional stuntman, playing with fire usually leaves people burnt. In a financial context this usually means the money is gone. Recommended Reading: Investopedia; Risk and Diversification: The Risk-Reward Tradeoff Investopedia; How to construct a High Risk portfolio Fidelity: Guide to Diversification KPMG: Understanding and articulating Risk Appetite (pdf)" "Diversification is spreading your investments around so that one point of risk doesn't sink your whole portfolio. The effect of having a diversified portfolio is that you've always got something that's going up (though, the corollary is that you've also always got something going down... winning overall comes by picking investments worth investing in (not to state the obvious or anything :-) )) It's worth looking at the different types of risk you can mitigate with diversification:  Company risk This is the risk that the company you bought actually sucks. For instance, you thought gold was going to go up, and so you bought a gold miner.  Say there are only two -- ABC and XYZ.  You buy XYZ. Then the CEO reveals their gold mine is played out, and the stock goes splat. You're wiped out. But gold does go up, and ABC does gangbusters, especially now they've got no competition.  If you'd bought both XYZ and ABC, you would have diversified your company risk, and you would have been much better off. Say you invested $10K, $5K in each. XYZ goes to zero, and you lose that $5K. ABC goes up 120%, and is now worth $11K. So despite XYZ bankrupting, you're up 10% on your overall position.  Sector risk You can categorize stocks by what ""sector"" they're in. We've already talked about one: gold miners. But there are many more, like utilities, bio-tech, transportation, banks, etc. Stocks in a sector will tend to move together, so you can be right about the company, but if the sector is out of favor, it's going to have a hard time going up.    Lets extend the above example. What if you were wrong about gold going up? Then XYZ would still be bankrupt, and ABC would be making less money so they went down as well; say, 20%. At that point, you've only got $4K left. But say that besides gold, you also thought that banks were cheap. So, you split your investment between the gold miners and a couple of banks -- lets call them LMN and OP -- for $2500 each in XYZ, ABC, LMN, and OP. Say you were wrong about gold, but right about banks; LMN goes up 15%, and OP goes up 40%.  At that point, your portfolio looks like this: XYZ start $2500 -100% end $0 ABC start $2500 +120% end $5500 LMN start $2500 +15% end $2875 OP start $2500 +40% end $3500 For a portfolio total of: $11,875, or a total gain of 18.75%.  See how that works?  Region/Country/Currency risk So, now what if everything's been going up in the USA, and everything seems so overpriced? Well, odds are, some area of the world is not over-bought. Like Brazil or England. So, you can buy some Brazilian or English companies, and diversify away from the USA. That way, if the market tanks here, those foreign companies aren't caught in it, and could still go up. This is the same idea as the sector risk, except it's location based, instead of business type based.  There is an additional twist to this -- currencies.  The Brits use the pound, and the Brazilians use the real. Most small investors don't think about this much, but the value of currencies, including our dollar, fluctuates. If the dollar has been strong, and the pound weak (as it has been, lately), then what happens if that changes? Say you own a British bank, and the dollar weakens and the pound strengthens. Even if that bank doesn't move at all, you would still make a gain.  Example: You buy British bank BBB for 40 pounds a share, when each pound costs $1.20. Say after a while, BBB is still 40 pounds/share, but the dollar weakened and the pound strengthened, such that each pound is now worth $1.50. You could sell BBB, and because of the currency exchange once you've got it converted back to dollars you'd have a 25% gain.   Market cap risk Sometimes big companies do well, sometimes it's small companies. The small caps are riskier but higher returning. When you think about it, small and mid cap stocks have much more ""room to run"" than large caps do. It's much easier to double a company worth $1 billion than it is to double a company worth $100 billion.  Investment types Stocks aren't the only thing you can invest in. There's also bonds, convertible bonds, CDs, preferred stocks, options and futures. It can get pretty complicated, especially the last two. But each of these investment behaves differently; and again the idea is to have something going up all the time.  The classical mix is stocks and bonds. The idea here is that when times are good, the stocks go up; when times are bad, the bonds go up (because they're safer, so more people want them), but mostly they're there to providing steady income and help keep your portfolio from cratering along with the stocks. Currently, this may not work out so well; stocks and bonds have been moving in sync for several years, and with interest rates so low they don't provide much income.  So what does this mean to you? I'm going make some assumptions here based on your post. You said single index, self-managed, and don't lower overall risk (and return). I'm going to assume you're a small investor, young, you invest in ETFs, and the single index is the S&P 500 index ETF -- SPY.  S&P 500 is, roughly, the 500 biggest companies in the USA. Further, it's weighted -- how much of each stock is in the index -- such that the bigger the company is, the bigger a percentage of the index it is.  If slickcharts is right, the top 5 companies combined are already 11% of the index! (Apple, Microsoft, Exxon, Amazon, and Johnson & Johnson). The smallest, News Corp, is a measly 0.008% of the index.  In other words, if all you're invested in is SPY, you're invested in a handfull of giant american companies, and a little bit of other stuff besides.  To diversify: Company risk and sector risk aren't really relevant to you, since you want broad market ETFs; they've already got that covered. The first thing I would do is add some smaller companies -- get some ETFs for mid cap, and small cap value (not small cap growth; it sucks for structural reasons). Examples are IWR for mid-cap and VBR for small-cap value.   After you've done that, and are comfortable with what you have, it may be time to branch out internationally. You can get ETFs for regions (such as the EU - check out IEV), or countries (like Japan - see EWJ). But you'd probably want to start with one that's ""all major countries that aren't the USA"" - check out EFA.  In any case, don't go too crazy with it. As index investing goes, the S&P 500 is not a bad way to go. Feed in anything else a little bit at a time, and take the time to really understand what it is you're investing in.  So for example, using the ETFs I mentioned, add in 10% each IWR and VBR. Then after you're comfortable, maybe add 10% EFA, and raise IWR to 20%. What the ultimate percentages are, of course, is something you have to decide for yourself.  Or, you could just chuck it all and buy a single Target Date Retirement fund from, say, Vanguard or T. Rowe Price and just not worry about it." "I would like to first point out that there is nothing special about a self-managed investment portfolio as compared to one managed by someone else. With some exceptions, you can put together exactly the same investment portfolio yourself as a professional investor could put together for you. Not uncommonly, too, at a lower cost (and remember that cost is among the, if not the, best indicator(s) of how your investment portfolio will perform over time). Diversification is the concept of not ""putting all your eggs in one basket"". The idea here is that there are things that happen together because they have a common cause, and by spreading your investments in ways such that not all of your investments have the same underlying risks, you reduce your overall risk. The technical term for risk is generally volatility, meaning how much (in this case the price of) something fluctuates over a given period of time. A stock that falls 30% one month and then climbs 40% the next month is more volatile than one that falls 3% the first month and climbs 4% the second month. The former is riskier because if for some reason you need to sell when it is down, you lose a larger portion of your original investment with the former stock than with the latter. Diversification, thus, is reducing commonality between your investments, generally but not necessarily in an attempt to reduce the risk of all investments moving in the same direction by the same amount at the same time. You can diversify in various ways: Do you see where I am going with this? A well-diversed portfolio will tend to have a mix of equity in your own country and a variety of other countries, spread out over different types of equity (company stock, corporate bonds, government bonds, ...), in different sectors of the economy, in countries with differing growth patterns. It may contain uncommon classes of investments such as precious metals. A poorly diversified portfolio will likely be restricted to either some particular geographical area, type of equity or investment, focus on some particular sector of the economy (such as medicine or vehicle manufacturers), or so on. The poorly diversified portfolio can do better in the short term, if you time it just right and happen to pick exactly the right thing to buy or sell. This is incredibly hard to do, as you are basically working against everyone who gets paid to do that kind of work full time, plus computer-algorithm-based trading which is programmed to look for any exploitable patterns. It is virtually impossible to do for any real length of time. Thus, the well-diversified portfolio tends to do better over time."
What decision are you trying to make?  Are you interested day trading stocks to make it rich? Or are you looking at your investment options and trying to decide between an actively managed mutual fund and an ETF? If the former, then precise statistics are hard to come by, but I believe that 99% of day traders would do better investing in an ETF. If the latter, then there are lots of studies that show that most actively managed funds do worse than index funds, so with most actively managed funds you are paying higher fees for worse performance.  Here is a quote from the Bogleheads Guide to Investing: Index funds outperform approximately 80 percent of all actively   managed funds over long periods of time. They do so for one simple   reason: rock-bottom costs. In a random market, we don't know what   future returns will be. However, we do know that an investor who keeps   his or her costs low will earn a higher return than one who does not.   That's the indexer's edge. Many people believe that your best option for investing is a diverse portfolio of ETFs, like this.  This is what I do. "A diversified portfolio (such as a 60% stocks / 40% bonds balanced fund) is much more predictable and reliable than an all-stocks portfolio, and the returns are perfectly adequate. The extra returns on 100% stocks vs. 60% are 1.2% per year (historically) according to https://personal.vanguard.com/us/insights/saving-investing/model-portfolio-allocations To get those average higher stock returns, you need to be thinking 20-30 years (even 10 years is too short-term). Over the 20-30 years, you must never panic and go to cash, or you will destroy the higher returns. You must never get discouraged and stop saving, or you will destroy the higher returns. You have to avoid the panic and discouragement despite the likelihood that some 10-year period in your 20-30 years the stock market will go nowhere. You also must never have an emergency or other reason to withdraw money early. If you look at ""dry periods"" in stocks, like 2000 to 2011, a 60/40 portfolio made significant money and stocks went nowhere. A diversified portfolio means that price volatility makes you money (due to rebalancing) while a 100% stocks portfolio means that price volatility is just a lot of stress with no benefit. It's somewhat possible, probably, to predict dry periods in stocks; if I remember the statistics, about 50% of the variability in the market price 10 years out can be explained by normalized market valuation (normalized = adjusted for business cycle and abnormal profit margins). Some funds such as http://hussmanfunds.com/ are completely based on this, though a lot of money managers consider it. With a balanced portfolio and rebalancing, though, you don't have to worry about it very much. In my view, the proper goal is not to beat the market, nor match the market, nor is it to earn the absolute highest possible returns. Instead, the goal is to have the highest chance of financing your non-financial goals (such as retirement, or buying a house). To maximize your chances of supporting your life goals with your financial decisions, predictability is more important than maximized returns. Your results are primarily determined by your savings rate - which realistic investment returns will never compensate for if it's too low. You can certainly make a 40-year projection in which 1.2% difference in returns makes a big difference. But you have to remember that a projection in which value steadily and predictably compounds is not the same as real life, where you could have emergency or emotional factors, where the market will move erratically and might have a big plunge at just the wrong time (end of the 40 years), and so on. If your plan ""relies"" on the extra 1.2% returns then it's not a reasonable plan anyhow, in my opinion, since you can't count on them. So why suffer the stress and extra risk created by an all-stocks portfolio?" "While it's definitely possible (and likely?) that a diversified portfolio generates higher returns than the S&P 500, that's not the main reason why you diversify. Diversification reduces risk.  Modern portfolio theory suggests that you should maximize return while reducing risk, instead of blindly chasing the highest returns. Think about it this way--say the average return is 11% for large cap US stocks (the S&P 500), and it's 10% for a diversified portfolio (say, 6-8 asset classes). The large cap only portfolio has a 10% chance of losing 30% in a given year, while the diversified portfolio has a 1% chance of losing 30% in a year. For the vast majority of investors, it's worth the 1% annual gap in expected return to greatly reduce their risk exposure. Of course, I just made those numbers up. Read what finance professors have written for the ""data and proof"". But modern portfolio theory is believed by a lot of investors and other finance experts. There are a ton of studies (and therefore data) on MPT--including many that contradict it." "You mentioned three concepts: (1) trading (2) diversification (3) buy and hold.   Trading with any frequency is for people who want to manage their investments as a hobby or profession.  You do not seem to be in that category.  Diversification is a critical element of any investment strategy.  No matter what you do, you should be diversified.  All the way would be best (this means owning at least some of every asset out there).  The usual way to do this is to own a mutual or index fund.  Or several.  These funds own hundreds or thousands of stocks, so that buying the fund instantly diversifies you. Buy and hold is the only reasonable approach to a portfolio for someone who is not interested in spending a lot of time managing it.  There's no reason to think a buy-and-hold portfolio will underperform a typical traded portfolio, nor that the gains will come later.  It's the assets in the portfolio that determine how aggressive/risky it is, not the frequency with which it is traded. This isn't really a site for specific recommendations, but I'll provide a quick idea:  Buy a couple of index funds that cover the whole universe of investments.  Index funds have low expenses and are the cheapest/easiest way to diversify.  Buy a ""total stock market"" fund and a ""total bond fund"" in a ratio that you like.  If you want, also buy an ""international fund.""  If you want specific tickers and ratios, another forum would be better(or just ask your broker or 401(k) provider).  The bogleheads forum is one that I respect where people are very happy to give and debate specific recommendations. At the end of the day, responsibly managing your investment portfolio is not rocket science and shouldn't occupy a lot of time or worry.  Just choose a few funds with low expenses that cover all the assets you are really interested in, put your money in them in a reasonable-ish ratio (no one knows that the best ratio is) and then forget about it." Diversification is just one aspect in an investment portfolio. The other aspects in Investment are Risk Taking Ability, Liquidity, Local Regulations, Tax benefits, Ease & Convenience, Cost of carrying out transactions etc. Investing in other regions is prone FX risk and other risks depending on the region of investment. For example investing in Emerging markets there is a risk of Local Regulations being changed, additional tax being levied, or Political instability and host of such risks.  Investing in local markets give you better understanding of such changes and the risk associated is less plus the Ease of carrying out transactions is great, less expensive compared to cost of transactions in other markets. Diversification in Investment should also be looked upon how much you invest in; Equities Debt Bullion Real Estate   Once you have a sizeable amount of investment in Equities or Debt, it would then make more sense to diversify this portion more to include funds from other regions. Unless you are an Running your own business, it makes sense to invest in your line of business if that is performing well. The reason being that the benefit / returns from the equities is much greater than the salary rise / bonus. For example I am in Information Technology and yet invest in all leading IT companies because the returns from companies in these segments have been good. Here would be the general steps to my mind for creating such a plan: Write out the final desired outcome. Is it $x in y years to fund your retirement? Is it $a in b years to put as a house down payment? This is the first step in defining how much money you want at what point in time. Consider what is your risk tolerance and how much time do you plan on spending in this plan. Is it rebalancing once a quarter and that's it or do you plan on doing monthly research and making tweaks all the time? This is slightly different from the first where one has to be mindful of how much volatility would one handle and what time commitment does one have for an investing strategy. Also, how much money would you be adding to the investments on what kind of time table would also be worth noting here. Construct the asset allocation based on the previous two steps along with historical returns averaged out to be a first draft of what you are buying in general. Is it US stocks? Is it a short-term bond fund? There are more than a few choices here that may make sense and it is worth considering based on the first couple of responses that determine what this will look like. Retirement in 40 years may be quite different than a house down payment in 2 years for example. Determine what brokerages or fund companies would offer such funds along with what types of accounts you'd want to have as in some countries there may be tax-advantaged accounts that may be useful to use here. This is where you're almost ready to start by doing the homework of figuring out how will things work. This may vary depending on one's jurisdiction. Get the applications from whatever institutions you'll be using and run with the desired asset allocation across various funds and accounts. Note that in the first few steps there were points of being aware of how much would you have, how aggressive are you investing and so forth. This is where you actually send in the money and get things rolling. Run with the plan and make tweaks as needed to achieve result, hopefully desired or better. A proper world porfolio is a non-trivial task. No one answer exists which is the best one and how one should construct it. World? The problem with world portfolio is that it is not well-defined. Providers use it as they wish and people use it as they wish, read the history for further ado (messy stuff). You can build yourself world portfolio but warning it is getting harder. You can use this tool by selecting global equity to search through global funds -- it is very useful and allows you to find the low-cost funds with PE/PB/Div.yield. Also, investigate topic more with this tool, less spam. "Funds - especially index funds - are a safe way for beginning investors to get a diversified investment across a lot of the stock market. They are not the perfect investment, but they are better than the majority of mutual funds, and you do not spend a lot of money in fees. Compared to the alternative - buying individual stocks based on what a friend tells you or buying a ""hot"" mutual fund - it's a great choice for a lot of people. If you are willing to do some study, you can do better - quite a bit better - with common stocks. As an individual investor, you have some structural advantages; you can take significant (to you) positions in small-cap companies, while this is not practical for large institutional investors or mutual fund managers.  However, you can also lose a lot of money quickly in individual stocks. It pays to go slow and to your homework, however, and make sure that you are investing, not speculating. I like fool.com as a good place to start, and subscribe to a couple of their newsletters. I will note that investing is not for the faint of heart; to do well, you may need to do the opposite of what everybody else is doing; buying when the market is down and selling when the market is high. A few people mentioned the efficient market hypothesis. There is ample evidence that the market is not efficient; the existence of the .com and mortgage bubbles makes it pretty obvious that the market is often not rationally valued, and a couple of hedge funds profited in the billions from this."