Will the popularity of index funds cause a pricing bubble in the stocks that make up an index?
With regard to commodity futures, a paper released in January 2010 by Aulerich, Irwin, and Garcia, concluded that index funds have essentially no impact on commodity futures. Looking at stocks, a stock that gets included in a major index does increase in price. It increases its turnover by 27% and increases its price by between 2.7% and 5.5%, according to information cited by Kula in this paper, though it looks like the price increase tends to happen in the lead up to the stock being included. Interestingly, I have read an article but cannot now locate it, which states that there's a measurable, albeit fairly small, price bubble on stocks included in common indexes, on Monday mornings, Friday afternoons, and at the start and end of the month. That is, the times when mutual funds are most likely to rebalance their holdings. This almost certainly applies to a lesser extent to other stocks, too. My understanding is that the price difference was very small, however. Generally speaking, stocks which make part of well-known indexes will tend to be in higher demand than stocks which do not. It remains the case that almost all actively-managed mutual funds are unable to consistently beat the indexes, even with this taken into account.
"One approach is to invest in ""allocation"" mutual funds that use various methods to vary their asset allocation. Some examples (these are not recommendations; just to show you what I am talking about): A good way to identify a useful allocation fund is to look at the ""R-squared"" (correlation) with indexes on Morningstar. If the allocation fund has a 90-plus R-squared with any index, it probably isn't doing a lot. If it's relatively uncorrelated, then the manager is not index-hugging, but is making decisions to give you different risks from the index. If you put 10% of your portfolio in a fund that varies allocation to stocks from 25% to 75%, then your allocation to stocks created by that 10% would be between 2.5% to 7.5% depending on the views of the fund manager. You can use that type of calculation to invest enough in allocation funds to allow your overall allocation to vary within a desired range, and then you could put the rest of your money in index funds or whatever you normally use. You can think of this as diversifying across investment discipline in addition to across asset class. Another approach is to simply rely on your already balanced portfolio and enjoy any downturns in stocks as an opportunity to rebalance and buy some stocks at a lower price. Then enjoy any run-up as an opportunity to rebalance and sell some stocks at a high price.  The difficulty of course is going through with the rebalance. This is one advantage of all-in-one funds (target date, ""lifecycle,"" balanced, they have many names), they will always go through with the rebalance for you - and you can't ""see"" each bucket in order to get stressed about it. i.e. it's important to think of your portfolio as a whole, not look at the loss in the stocks portion. An all-in-one fund keeps you from seeing the stocks-by-themselves loss number, which is a good way to trick yourself into behaving sensibly. If you want to rebalance ""more aggressively"" then look at value averaging (search for ""value averaging"" on this site for example). A questionable approach is flat-out market-timing, where you try to get out and back in at the right times; a variation on this would be to buy put options at certain times; the problem is that it's just too hard. I think it makes more sense to buy an allocation fund that does this for you. If you do market time, you want to go in and out gradually, and value averaging is one way to do that." As has been pointed out, one isn't cheaper than the other. One may have a lower price per share than the other, but that's not the same thing. Let's pretend that the total market valuation of all the stocks within the index was $10,000,000. (Look, I said let's pretend.) You want to invest $1,000. For the time being, let's also pretend that your purchasing 0.01% of all the stock won't affect prices anywhere. One company splits the index into 10,000 parts worth $1,000 each. The other splits the same index into 10,000,000 parts worth $1 each. Both track the underlying index perfectly. If you invest $1,000 with the first company, you get one part; if you invest $1,000 with the second, you get 1,000 parts. Ignoring spreads, transaction fees and the like, immediately after the purchase, both are worth exactly $1,000 to you. Now, suppose the index goes up 2%. The first company's shares of the index (of which you would have exactly one) are now worth $1,020 each, and the second company's shares of the index (of which you would have exactly 1,000) are worth $1.02 each. In each case, you now have index shares valued at $1,020 for a 2% increase ($1,020 / $1,000 = 1.02 = 102% of your original investment). As you can see, there is no reason to look at the price per share unless you have to buy in terms of whole shares, which is common in the stock market but not necessarily common at all in mutual funds. Because in this case, both funds track the same underlying index, there is no real reason to purchase one rather than the other because you believe they will perform differently. In an ideal world, the two will perform exactly equally. The way to compare the price of mutual funds is to look at the expense ratio. The lower the expense ratio is, the cheaper the fund is, and the less of your money is being eroded every day in fees. Unless you have some very good reason to do differently, that is how you should compare the price of any investment vehicles that track the same underlying commodity (in this case, the S&P 500). "Funds which track the same index may have different nominal prices.  From an investors point of view, this is not important.  What is important is that when the underlying index moves by a given percentage, the price of the tracking funds also move by an equal percentage.  In other words, if the S&P500 rises by 5%, then the price of those funds tracking the S&P500 will also rise by 5%.  Therefore, investing a given amount in any of the tracking funds will produce the same profit or loss, regardless of the nominal prices at which the individual funds are trading. To see this, use the ""compare"" function available on the popular online charting services. For example, in Google finance call up a chart of the S&P500 index, then use the compare textbox to enter the codes for the various ETFs tracking the S&P500.  You will see that they all track the S&P500 equally so that your relative returns will be equal from each of the tracking funds.  Any small difference in total returns will be attributable to management fees and expenses, which is why low fees are so important in passive investing." "I actually love this question, and have hashed this out with a friend of mine where my premise was that at some volume of money it must be advantageous to simply track the index yourself. There some obvious touch-points: Most people don't have anywhere near the volume of money required for even a $5 commission outweigh the large index fund expense ratios. There are logistical issues that are massively reduced by holding a fund when it comes to winding down your investment(s) as you get near retirement age. Index funds are not touted as categorically ""the best"" investment, they are being touted as the best place for the average person to invest. There is still a management component to an index like the S&P500.  The index doesn't simply buy a share of Apple and watch it over time.  The S&P 500 isn't simply a single share of each of the 500 larges US companies it's market cap weighted with frequent rebalancing and constituent changes.  VOO makes a lot of trades every day to track the S&P index, ""passive index investing"" is almost an oxymoron. The most obvious part of this is that if index funds were ""the best"" way to invest money Berkshire Hathaway would be 100% invested in VOO.  The argument for ""passive index investing"" is simplified for public consumption.  The reality is that over time large actively managed funds have under-performed the large index funds net of fees.  In part, the thrust of the advice is that the average person is, or should be, more concerned with their own endeavors than they are managing their savings.  Investment professionals generally want to avoid ""How come I my money only returned 4% when the market index returned 7%?  If you track the index, you won't do worse than the index; this helps people sleep better at night. In my opinion the dirty little secret of index funds is that they are able to charge so much less because they spend $0 making investment decisions and $0 on researching the quality of the securities they hold.  They simply track an index; XYZ company is 0.07% of the index, then the fund carries 0.07% of XYZ even if the manager thinks something shady is going on there. The argument for a majority of your funds residing in Mutual Funds/ETFs is simple, When you're of retirement age do you really want to make decisions like should I sell a share of Amazon or a share of Exxon?  Wouldn't you rather just sell 2 units of SRQ Index fund and completely maintain your investment diversification and not pay commission?  For this simplicity you give up three basis points?  It seems pretty reasonable to me." ETFs have caused many if not most stocks on the SP500 to become correlated.  I think at some point in the last couple of years, 90% of the SP500 were correlated to the index itself.  So you're going to see a lot of movement together of most stocks. An index will drop a company for several reasons:  A fund decides how close they want to mirror the index. Some do so exactly, others only approximate the index. You can look at it from a fundamental perspective to see who benefits from rising oil prices. That's a high level analysis and the devil is in the details - higher oil prices may favour electric car producers for example or discount clothes retailers vs. branded clothes manufacturers. Another approach it to use a statistical analysis. I have run a quick and dirty correlation of the various S&P sector indices against the oil prices (Crude). Based on the the results below, you would conclude that materials and energy stocks should perform well with rising oil prices. There again, it is a behaviour you would expect at the group level but it may not translate to each individual company within those groups (in particular in the materials sector where some would benefit and some would be detrimentally affected). You could get exposure to those sectors using ETFs, such as XLB and XLE in the US. Or you could run the same analysis for each stock within the S&P 500 (or whatever index you are looking at) and create a portfolio with the stocks that are the most correlated with oil prices. This is calculated over 10 years of monthly returns after removing the market component from the individual sectors. The two important columns are: The point of buying an index fund is that you don't have to pick winners. As long as the winners are included in the index fund (which can include far more than 500 stocks), you benefit on average because of overall upward historical market performance. Picking only the top 50 capitalized stocks in the S&P 500 does not guarantee you will successfully track the S&P 500 index because the stocks in the tail can account for an outsized amount of overall growth; the top 50 stocks by market capitalization change over time, and these stocks are not necessarily the stocks that perform better.  As direct example, the 10 year average annual return for the S&P top 50 is 4.52%, while the 10 year average annual return for the S&P 500 is 5.10%. Issues of trading and balancing to maintain these aside, these indices are not the same.