At what point do index funds become unreliable?
"A great deal of analysis on this question relies on misunderstandings of the market or noticing trends that happened at the same time but were not caused by each other.  Without knowing your view, I'll just give the basic idea. The amount of active management is self-correcting.  The reason people have moved out of actively managed funds is that the funds have not been performing well.  Their objective is to beat their benchmarks by profiting as they correct mispricing.  They are performing poorly because there is too much money chasing too few mispricings.  That is why the actively managed industry is shrinking.  If it gets small enough, presumably those opportunities will become more abundant and mispricing correction will become more profitable.  Then money will flow back into active funds. Relevant active management may not be what a lay person is thinking of.  At the retail level, we are observing a shift to passive funds, but there is still plenty of money in other places.  For example, pension and endowment funds normally have an objective of beating a market benchmark like the Russell 3000.  As a result they are constantly trying to find opportunities to invest in active management that really can outperform.  They represent a great deal of money and are nothing like the ""buy and forget"" stereotype we sometimes imagine.  Moreover, hedge funds and propreitary trading shops explicitly and solely try to correct mispricings.  They represent a very, very large bucket of money that is not shrinking.  Active retail mutual funds and individual investors are not as relevant for pricing as we might think.  More trading volume is not necessarily a good thing, nor is it the measure of market quality.  One argument against passive funds is that passive funds don't trade much.  Yet the volume of trading in the markets has risen dramatically over time as a result of technological improvements (algorithmic traders, mostly).  They have out-competed certain market makers who used to make money on inefficiencies of the market.  Is this a good thing or a bad thing?  Well, prices are more efficient now and it appears that these computers are more responsive to price-relevant information than people used to be.  So even if trading volume does decrease, I see no reason to worry that prices will become less efficient.  That's not the direction things have gone, even as passive investing has boomed. Overall, worries about passive investing rely on an assumption that there is not enough interest in and resources for making arbitrage profits to keep prices efficient.  This is highly counterfactual and always will be.  As long as people and institutions want money and have access to the markets, there will be plenty of resources allocated to price correction." "The argument you are making here is similar to the problem I have with the stronger forms of the efficient market hypothesis.  That is if the market already has incorporated all of the information about the correct prices, then there's no reason to question any prices and then the prices never change.  However, the mechanism through which the market incorporates this information is via the actors buying an selling based on what they see as the market being incorrect. The most basic concept of this problem (I think) starts with the idea that every investor is passive and they simply buy the market as one basket.  So every paycheck, the index fund buys some more stock in the market in a completely static way.  This means the demand for each stock is the same.  No one is paying attention to the actual companies' performance so a poor performer's stock price never moves.  The same for the high performer.  The only thing moving prices is demand but that's always up at a more or less constant rate. This is a topic that has a lot of discussion lately in financial circles.  Here are two articles about this topic but I'm not convinced the author is completely serious hence the ""worst-case scenario"" title. These are interesting reads but again, take this with a grain of salt.  You should follow the links in the articles because they give a more nuanced understanding of each potential issue.  One thing that's important is that the reality is nothing like what I outline above. One of the links in these articles that is interesting is the one that talks about how we now have more indexes than stocks on the US markets.  The writer points to this as a problem in the first article, but think for a moment why that is.  There are many different types of strategies that active managers follow in how they determine what goes in a fund based on different stock metrics.  If a stocks P/E ratio drops below a critical level, for example, a number of indexes are going to sell it.  Some might buy it.  It's up to the investors (you and me) to pick which of these strategies we believe in. Another thing to consider is that active managers are losing their clients to the passive funds.  They have a vested interest in attacking passive management." "As more actively managed funds are driven out of the market, the pricing of individual stocks should become less rational. I.e. more stocks will become underpriced relative to their peers. As stock prices become less rational, the reward for active investing will increase, since it will become easier to ""pick a winner"". Eventually, the market will reach a new equilibrium where only active investors who are good enough to turn a profit will remain. Even then, passive investment will still do roughly as well as ""the market"" since it has low overhead and minimal investment lag. There is no reason to expect the system to collapse, since it is characterized primarily by negative feedback loops rather than positive feedback.  The last few decades have seen a shift from active to passive investment because increased market transparency and efficiency have reduced the labor required to keep pricing rational. Basically, as people have gotten better at predicting stock performance, less active investment has been required to keep prices rational." "private investors that don't have the time or expertise for active investment.  This may be known as every private investor. An index fund ensures average returns. The bulk of active trading is done by private institutions with bucketloads of experts studying the markets and AI scraping every bit of data it can get (from the news, stock market, the weather reports, etc...). Because of that, to get above average returns an average percent of the time, singular private investors have to drastically beat the average large team of individuals/software. Now that index ETF are becoming so fashionable, could there be a tipping point at which the market signals that active investors send become so diluted that this ""index ETF parasitism"" collapses? How would this look like and would it affect only those who invest in index ETF or would it affect the stock market more generally? To make this question perhaps more on-topic: Is the fact (or presumption) that index ETF rely indirectly on active investment decisions by other market participants, as explained above, a known source of concern for personal investment? This is a well-covered topic. Some people think this will be an issue.   Others point out that it is a hard issue to bootstrap. I gravitate to this view. A small active market can support a large number of passive investors. If the number of active investors ever got too low, the gains & likelihood of gains that could be made from being an active investor would rise and generate more active investors. Private investing makes sense in a few cases. One example is ethics. Some people may not want to be invested, even indirectly, in certain companies." Private investors as mutual funds are a minority of the market.  Institutional investors make up a substantial portion of the long term holdings.  These include pension funds, insurance companies, and even corporations managing their money, as well as individuals rich enough to actively manage their own investments.   From Business Insider, with some aggregation:   Numbers don't add to 100% because of rounding.  Also, I pulled insurance out of household because it's not household managed.  Another source is the Tax Policy Center, which shows that about 50% of corporate stock is owned by individuals (25%) and individually managed retirement accounts (25%).   Another issue is that household can be a bit confusing.  While some of these may be people choosing stocks and investing their money, this also includes Employee Stock Ownership Plans (ESOP) and company founders.  For example, Jeff Bezos owns about 17% of Amazon.com according to Wikipedia.  That would show up under household even though that is not an investment account.  Jeff Bezos is not going to sell his company and buy equity in an index fund.   Anyway, the most generous description puts individuals as controlling about half of all stocks.  Even if they switched all of that to index funds, the other half of stocks are still owned by others.  In particular, about 26% is owned by institutional investors that actively manage their portfolios.   In addition, day traders buy and sell stocks on a daily basis, not appearing in these numbers.  Both active institutional investors and day traders would hop on misvalued stocks, either shorting the overvalued or buying the undervalued.   It doesn't take that much of the market to control prices, so long as it is the active trading market.  The passive market doesn't make frequent trades.  They usually only need to buy or sell as money is invested or withdrawn.  So while they dominate the ownership stake numbers, they are much lower on the trading volume numbers.   TL;DR:  there is more than enough active investment by organizations or individuals who would not switch to index funds to offset those that do.  Unless that changes, this is not a big issue.
I researched quite a bit around this topic, and it seems that this is indeed false. Long ter asset growth does not converge to the compound interest rate of expected return. While it is true that standard deviations of annualized return decrease over time, because the asset value itself changes over time, the standard deviations of the total return actually increases.      Thus, it is wrong to say that you can take increased risk because you have a longer time horizon.  Source "This falls under value investing, and value investing has only recently picked up study by academia, say, at the turn of the millennium; therefore, there isn't much rigorous on value investing in academia, but it has started. However, we can describe valuations: In short, valuations are randomly distributed in a log-Variance Gamma fashion with some reason & nonsense mixed in. You can check for yourself on finviz.  You can basically download the entire US market and then some, with many financial and technical characteristics all in one spreadsheet. Re Fisher: He was tied for the best monetary economist of the 20th century and created the best price index, but as for stocks, he said this famous quote 12 days before the 1929 crash: ""Stock prices have reached what looks like a permanently high plateau. I do not feel there will be soon if ever a 50 or 60 point break from present levels, such as (bears) have predicted. I expect to see the stock market a good deal higher within a few months.""   - Irving Fisher, Ph.D. in economics, Oct. 17, 1929 EDIT Value investing has almost always been ignored by academia.  Irving Fisher and other proponents of it before it was codified by Graham in the mid 20th century certainly didn't help with comments like the above.  It was almost always believed that it was a sucker's game, ""the bigger sucker"" game to be more precise because value investors get destroyed during recession/collapses.  So even though a recessionless economy would allow value investors and everyone never to suffer spontaneous collapses, value investors are looked down upon by academia because of the inevitable yet nearly always transitory collapse.  This expresses that sentiment perfectly. It didn't help that Benjamin Graham didn't care about money so never reached the heights of Buffett who frequently alternates with Bill Gates as the richest person on the planet.  Buffett has given much credibility, and academia finally caught on around in 2000 or so after he was proven right about a pending tech collapse that nearly no one believed would happen; at least, that's where I begin seeing papers being published delving into value concepts.  If one looks harder, academia's even taken the torch and discovered some very useful tools. Yes, investment firms and fellow value investors kept up the information publishing, but they are not academics. The days of professors throwing darts at the stock listings and beating active managers despite most active managers losing to the market anyways really held back this side of academia until Buffett entered the fray and embarrassed them all with his club's performance, culminating in the Superinvestors article which is still relatively ignored.  Before that, it was the obsession with beta, the ratio of a security's variance to its covariance to the market, a now abandoned theory because it has been utterly discredited; the popularizers of beta have humorously embraced the P/B, not giving the satisfaction to Buffet by spurning the P/E.   Tiny technology firms receive ridiculous valuations because a long-surviving tiny tech firm usually doesn't stay small for long thus will grow at huge rates.  This is why any solvent and many insolvent tech firms receive large valuations: risk-adjusted, they should pay out huge on average.  Still, most fall by the wayside dead, and those 100 P/S valuations quickly crumble. Valuations are influenced by growth.  One can see this expressed more easily with a growing perpetuity: Where P is price, i is income, r is the rate of return, and g is the growth rate of i.  Rearranging, r looks like: Here, one can see that a higher P relative to i will dull the expected rate of return while a higher g will boost it. It's fun for us value investor/traders to say that the market is totally inefficient.  That's a stretch.  It's not perfectly inefficient, but it's efficient.  Valuations are clustered very tightly around the median, but there are mistakes that even us little guys can exploit and teach the smart money a lesson or two. If one were to look at a distribution of rs, one'd see that they're even more tightly packed.  So while it looks like P/Es are all over the place industry to industry, rs are much more well clustered. Tech, finance, and discretionaries frequently have higher growth rates so higher P/Es yet average rs.  Utilities and non-discretionaries have lower growth rates so lower P/Es yet average rs." If you throw up a 20 year chart on the 10 year you can see it isn't fluctuating around 2%.  It happens to be at 2% now but it has been relentlessly driving lower for at least 20 years.  My own personal biased opinion is that it is a market infested with ultra-wealthy people who aren't looking for returns.  They just basically want to maintain what they already sucked out of the system. "Being long the S&P Index ETF you can expect to make money. The index itself will never ""crash"" because the individual stocks in it are simply removed when they begin performing badly. This is not to say that the S&P Index won't lose 80% of its value in an instant (or over a few trading sessions if circuit breakers are considered), but even in the 2008 correction, the S&P still traded far above book value. With this in mind, you have to realize, that despite common sentiment, the indexes are hardly representative of ""the market"". They are just a derivative, and as you might be aware, derivatives can enable financial tricks far removed from reality. Regarding index funds, if a small group of people decide that 401k's are performing badly, then they will simply rebalance the components of the indexes with companies that are doing well. The headline will be ""S&P makes ANOTHER record high today"" So although panic selling can disrupt the order book, especially during periods of illiquidity, with the current structure ""the stock market"" being based off of three composite indexes, can never crash, because there will always exist a company that is not exposed to broad market fluctuations and will be performing better by fundamentals and share price. Similarly, you collect dividends from the index ETFs. You can also sell covered calls on your holdings. The CBOE has a chart through the 2008 crisis showing your theoretical profit and loss if you sold calls 2 standard deviations out of the money, at every monthly interval. If you are going to be holding an index ETF for a long time, then you shouldn't be concerned about its share price at all, since the returns would be pretty abysmal either way, but it should suffice for hedging inflation." By all measures, the U.S. stock market is currently frothy. The apparent stability of the world financial system is superficial – financial asset prices are not real, the equilibrium is temporary, the lack of volatility is a trap, and when the whole thing goes haywire, there will truly be hell to pay. The volatility of an index fund should usually be a lot lower than that of an individual stock. However even with a broad index fund you should consider the fact that being down by 10% in the time frame you refer to is quite possible! So is being up by 10% of course. A corporate bond might be a better choice if you can find one you trust. great example of levered tracking error is any 2x/3x VIX etf. during periods of high volatility (like last week) you will be able to realize much higher returns on the underlying index as the levered and inverse ETFs are unable to replicate their intended performance using market securities.  it is not uncommon to see the VIX up ~30% with levered ETFs only netting ~10-12% as opposed to the intended 60 or 90%, for example "The problem with the proposed plan is the word ""inevitable"". There is no such thing as a recovery that is guaranteed (though we may wish it to be so), and even if there was there is no telling how long it will take for a recovery to occur to a sufficient degree. There are also no foolproof ways to determine when you have hit the bottom. For historical examples, consider the Nikkei. In 2000 the value fell from 20000 to 15000 in a single year. Had you bought then, you would have found the market still fell and didn't get back to 15k until 2005...where it went up and down for years, when in 2008 it fell again and would not get back to that level again until 2014. Lest you think this was an isolated international incident, the same issues happened to the S&P in 2002, where things went up until they fell even lower in 2009 before finally climbing again.  Will there be another recession at some point? Surely. Will there be a single, double, or triple dip, and at what point is the true bottom - and will it take 5, 10, or 20+ years for things to get back above when you bought? No one really knows, and we can only guess.  So if you want to double down after a recession, you can, but it's important you not fool yourself into thinking you aren't greatly increasing your risk exposure, because you are." If you are investing for 10 years, then you just keep buying at whatever price the fund is at. This is called dollar-cost averaging. If the fund is declining in value from when you first bought it, then when you buy more, the AVERAGE price you bought in at is now lower. So therefore your losses are lower AND when it goes back up you will make more. Even if it continues to decline in value then you keep adding more money in periodically, eventually your position will be so large that on the first uptick you will have a huge percent gain. Anyway this is only suggested because you are in it for 10 years. Other people's investment goals vary. "Once you buy stocks on X day of the month, the chances of stocks never actually going above and beyond your point of value on the chart are close to none. How about Enron?  GM? WorldCom? Lehman Brothers?  Those are just a few of the many stocks that went to 0.  Even stock in solvent companies have an ""all-time high"" that it will never reach again.   Please explain to my why my thought is [in]correct.  It is based on flawed assumptions, specifically that stock always regain any losses from any point in time.  This is not true.  Stocks go up and down - sometimes that have losses that are never made up, even if they don't go bankrupt.  If your argument is that you should cash out any gains regardless of size, and you will ""never lose"", I would argue that you might have very small gains in most cases, but there are still times where you are going to lose value and never regain it, and those losses can easily wipe out any gains you've made.   Never bought stocks and if I try something stupid I'll lose my money, so why not ask the professionals first..? If you really believe that you ""can't lose"" in the stock market then do NOT buy individual stocks.  You may as well buy a lottery ticket (not really, those are actually worthless).  Stick to index funds or other stable investments that don't rely on the performance of a single company and its management.  Yes, diversification reduces (not eliminates) risk of losses.  Yes, chasing unreasonable gains can cause you to lose.  But what is a ""reasonable gain""?  Why is your ""guaranteed"" X% gain better than the ""unreasonable"" Y% gain? How do you know what a ""reasonable"" gain for an individual stock is?" "Yes, many hedge funds (for example) did not survive 2008-2009.  But hedge funds were failing both before and after that period, and other hedge funds thrived.  Those types of funds are particularly risky because they depend so much on leverage (i.e. on money that isn't actually theirs). More publically-visible funds (like those of the big-name index fund companies) tended not to close because they are not leveraged.  You say that ""a great many companies"" failed during the recession, but that's not actually true.  I can't think of more than a handful of publically-traded companies that went bankrupt.  So, since the vast majority of publically-traded companies stayed in business, their stocks kept some/most of their value, and the funds that owned those stocks stayed afloat. I personally did not see a single index fund that went out of business due to the recession." Your asset mix should reflect your own risk tolerance.  Whatever the ideal answer to your question, it requires you to have good timing, not once, but twice. Let me offer a personal example. In 2007, the S&P hit its short term peak at 1550 or so. As it tanked in the crisis, a coworker shared with me that he went to cash, on the way down, selling out at about 1100. At the bottom, 670 or so, I congratulated his brilliance (sarcasm here) and as it passed 1300 just 2 years later, again mentions how he must be thrilled he doubled his money. He admitted he was still in cash. Done with stocks. So he was worse off than had he held on to his pre-crash assets. For sake of disclosure, my own mix at the time was 100% stock. That's not a recommendation, just a reflection of how my wife and I were invested.  We retired early, and after the 2013 excellent year, moved to a mix closer to 75/25. At any time, a crisis hits, and we have 5-6 years spending money to let the market recover. If a Japanesque long term decline occurs, Social Security kicks in for us in 8 years.  If my intent wasn't 100% clear, I'm suggesting your long term investing should always reflect your own risk tolerance, not some short term gut feel that disaster is around the corner. The issue is the time frame. With a one year investment horizon the only way for a fund manager to be confident that they are not going to lose their shirt is to invest your money in ultra conservative low volatility investments. Otherwise a year like 2008 in the US stock market would break them. Note if you are willing to expand your payback time period to multiple years then you are essentially looking at an annuity and it's market loss rider. Of course those contacts are always structured such that the insurance company is extremely confident that they will be able to make more in the market than they are promising to pay back (multiple decade time horizons). "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." The only way for a mutual fund to default is if it inflated the NAV. I.e.: it reports that its investments worth more than they really are. Then, in case of a run on the fund, it may end up defaulting since it won't have the money to redeem shares at the NAV it published. When does it happen? When the fund is mismanaged or is a scam. This happened, for example, to the fund Madoff was managing. This is generally a sign of a Ponzi scheme or embezzlement. How can you ensure the funds you invest in are not affected by this? You'll have to read the fund reports, check the independent auditors' reports and check for clues. Generally, this is the job of the SEC - that's what they do as regulators. But for smaller funds, and private (i.e.: not public) investment companies, SEC may not be posing too much regulations.