Why is the price of my investment only updated once per day?
Mutual funds are collections of investments that other people pay to join.  It would be simpler to calculate the value of all these investments at one time each day, and then to deem that any purchases or sales happen at that price.  The fund diversifies rather than magnifies risk, looking to hold rather than enjoy a quick turnaround.  Nobody really needs hourly updated price information for an investment they intend to hold for decades. They quote their prices on a daily basis and you take the daily price.  This makes sense for a vehicle that is a balanced collection of many different assets, most of which will have varying prices over the course a day.  That makes pricing complicated.  This primer explains mutual fund pricing and the requirements of the Investment Company Act of 1940, which mandates daily price reporting.  It also illustrates the complexity: How does the fund pricing process work? Mutual fund pricing is an intensive process that takes place in a short time frame at the end of the day. Generally, a fund’s pricing process begins at the close of the New York Stock Exchange, normally 4 p.m. Eastern time. The fund’s accounting agent, which may be an affiliated entity such as the fund’s adviser, or a third-party servicer such as the fund’s administrator or custodian bank, is usually responsible for calculating the share price. The accounting agent obtains prices for the fund’s securities from pricing services and directly from brokers. Pricing services collect securities prices from exchanges, brokers, and other sources and then transmit them to the fund’s accounting agent. Fund accounting agents internally validate the prices received by subjecting them to various control procedures. For example, depending on the nature and extent of its holdings, a fund may use one or more pricing services to ensure accuracy. Note that under Rule 22c-1 forward pricing, fund shareholders receive the next daily price, not the last daily price.  Forward pricing makes sense if you want shareholders to get the most accurate sale or purchase price, but not if you want purchasers and sellers to be able to make precise calculations about gains and losses (how can you be precise if the price won't be known until after you buy or sell?). Mutual funds are only traded once per day, while other securities can be traded any time during the day. Mutual funds are actually a collection of other things that have value, such as stocks. The price of a mutual fund is calculated at the end of the day after the market closes by looking at how much the collection of things changed in value during the day. I strongly suggest you go to www.investor.gov as it has excellent information regarding these types of questions. A mutual fund is a company that pools money from many investors and invests the money in securities such as stocks, bonds, and short-term debt. The combined holdings of the mutual fund are known as its portfolio. Investors buy shares in mutual funds. Each share represents an investor’s part ownership in the fund and the income it generates. When you buy shares of a mutual fund you're buying it at NAV, or net asset value.  The NAV is the value of the fund’s assets minus its liabilities. SEC rules require funds to calculate the NAV at least once daily. Different funds may own thousands of different stocks.  In order to calculate the NAV, the fund company must value every security it owns.  Since each security's valuation is changing throughout the day it's difficult to determine the valuation of the mutual fund except for when the market is closed.  Once the market has closed (4pm eastern) and securities are no longer trading, the company must get accurate valuations for every security and perform the valuation calculations and distribute the results to the pricing vendors.  This has to be done by 6pm eastern.  This is a difficult and, more importantly, a time consuming process to get it done right once per day.  Having worked for several fund companies I can tell you there are many days where companies are getting this done at the very last minute. When you place a buy or sell order for a mutual fund it doesn't matter what time you placed it as long as you entered it before 4pm ET.  Cutoff times may be earlier depending on who you're placing the order with.  If companies had to price their funds more frequently, they would undoubtedly raise their fees. Mutual funds are a collection of other assets, such as stocks, bonds and property. Unless the fund is a type that is traded on an exchange, you will only be able to buy into the fund by applying for units with the fund manager and sell out by contacting the fund manager. These type of non-traded funds are usually updated at the end of the day once the closing prices of all the assets in it are known. "There is no fundamental, good reason, I think; ""that's just how it's done"" (which is what all the other answers seem to be saying, w/o coming out and admitting it). Just guessing, but I'll bet most of the reason is historical: Before up-to-the-moment quotes were readily available, that was a bit tedious to calculate/update the fund's value, so enacted-laws let it be done just once per day.  (@NL7 quotes the security act of 1940, which certainly has been updated, but also still might contain the results of crufty rationales, like this.) There are genuinely different issues between funds and stocks, though: One share of a fund is fundamentally different from one share of stock: There is a finite supply of Company-X-stock, and people are trading that piece of ownership around, and barter to find an mutually-agreeable-price.  But when you buy into a mutual-fund, the mutual-fund ""suddenly has more shares"" -- it takes your money and uses it to buy shares of the underlying stocks (in a ratio equal to its current holdings).  As a consequence: the mutual fund's price isn't determined by two people bartering and agreeing on a price (like stock); there is exactly one sane way to price a mutual fund, and that's the weighted total of its underlying stock.  If you wanted to sell your ownership-of-Mutual-Fund-Z to a friend at 2:34pm, there wouldn't be any bartering, you'd just calculate the value based on the stated-value of the underlying stock at that exact moment. So: there's no inherent reason you can't instantaneously price a mutual fund.  BUT people don't really buy/sell funds to each other -- they go to the fund-manager and essentially make a deposit-or-withdraw.  The fund-manager is only required by law to do it once a day (and perhaps even forbidden from doing it more often?), so that's all they do. [Disclaimer: I know very little about markets and finance. But I recognize answers that are 'just because'.]"
I work on a buy-side firm, so I know how these small data issues can drive us crazy. Hope my answer below can help you:  Reason for price difference: 1. Vendor and data source Basically, data providers such as Google and Yahoo redistribute EOD data by aggregating data from their vendors. Although the raw data is taken from the same exchanges, different vendors tend to collect them through different trading platforms. For example, Yahoo, is getting stock data from Hemscott (which was acquired by Morningstar), which is not the most accurate source of EOD stocks. Google gets data from Deutsche Börse.  To make the process more complicated, each vendor can choose to get EOD data from another EOD data provider or the exchange itself, or they can produce their own open, high, low, close and volume from the actual trade tick-data, and these data may come from any exchanges.  2. Price Adjustment  For equities data, the re-distributor usually adjusts the raw data by applying certain customized procedures. This includes adjustment for corporate actions, such as dividends and splits. For futures data, rolling is required, and back-ward and for-warding rolling can be chosen. Different adjustment methods can lead to different price display.  3. Extended trading hours  Along with the growth of electronic trading, many market tends to trade during extended hours, such as pre-open and post-close trading periods. Futures and FX markets even trade around the clock. This leads to another freedom in price reporting: whether to include the price movement during the extended trading hours.   Conclusion To cross-verify the true price, we should always check the price from the Exchange where the asset is actually traded. Given the convenience of getting EOD data nowadays, this task should be easy to achieve.  In fact, for professional traders and investors alike, they will never reply price on free providers such as Yahoo and Google, they will most likely choose Bloomberg, Reuters, etc. However, for personal use, Yahoo and Google should both be good choices, and the difference is small enough to ignore. The last column in the source data is volume (the number of stocks that was exchanged during the day), and it also has a value of zero for that day, meaning that nobody bought or sold the stocks on that day. And since the prices are prices of transactions (the first and the last one on a particular day, and the ones with the highest/lowest price), the prices cannot be established, and are irrelevant as there was not a single transaction on that day. Only the close price is assumed equal to its previous day counterpart because this is the most important value serving as a basis to determine the daily price change (and we assume no change in this case). Continuous-line charts also use this single value. Bar and candle charts usually display a blank space for a day where no trade occurred. It does sometimes open one day the same as it closed the previous day.  Take a look at ESCA, it closed October 29th at 4.50, at opened November 1st at 4.50.  It's more likely to change prices overnight than it is between two successive ticks during the day, because a lot more time passes, in which news can come out, and in which people can reevaluate the stock. The dynamics of different contracts and liquidity can be quite different on the last day on the month and for intraday trade make sure you use bid-ask data as opposed to historical trades.  I'm not saying whether it works or not, but im just giving you ideas to improve your testing. All the time. For high volume stocks, it may be tough to see exactly what's going on, e.g. the bid/ask may be moving faster than your connection to the broker can show you.  What I've observed is with options. The volume on some options is measured in the 10's or 100's of contracts in a day. I'll see a case where it's $1.80/$2.00 bid/ask, and by offering $1.90 will often see a fill at that price. Since I may be the only trade on that option in the 15 minute period and note that the stock wasn't moving more than a penny during that time, I know that it was my order that managed to fill between the bid/ask. You bought 1 share of Google at $67.05 while it has a current trading price of $1204.11. Now, if you bought a widget for under $70 and it currently sells for over $1200 that is quite the increase, no? Be careful of what prices you enter into a portfolio tool as some people may be able to use options to have a strike price different than the current trading price by a sizable difference. Take the gain of $1122.06 on an initial cost of $82.05 for seeing where the 1367% is coming. User error on the portfolio will lead to misleading statistics I think as you meant to put in something else, right? The short float ratio and percent change are all calculated based on the short interest (the total number of shares shorted).  The short interest data for Nasdaq and NYSE stocks is published every two weeks. NasdaqTrader.com shows the exact dates for when short interest is published for Nasdaq stocks, and also says the following: FINRA member firms are required to report their short positions as of settlement on (1) the 15th of each month, or the preceding business day if the 15th is not a business day, and (2) as of settlement on the last business day of the month.* The reports must be filed by the second business day after the reporting settlement date. FINRA compiles the short interest data and provides it for publication on the 8th business day after the reporting settlement date. The NYSE also shows the exact dates for when short interest is published for NYSE stocks, and those dates are exactly the same as for Nasdaq stocks. Since the short interest is only updated once every 2 weeks, there is no way to see real-time updating of the short float and percent change.  That information only gets updated once every 2 weeks - after each publication of the short interest. "The price of a company's stock at any given moment is established by a ratio of buyers to sellers.  When the sellers outnumber the buyers at a given price, the stock price drops until there are enough people willing to buy the stock to balance the equation again.  When there are more people wanting to purchase a stock at a given price than people willing to sell it, the stock price rises until there are enough sellers to balance things again.  So given this, it's easy to see that a very large fund (or collection of very large funds) buying or selling could drive the price of a stock in one direction or another (because the sheer number of shares they trade can tip the balance one way or another).   What's important to keep in mind though is that the ratio of buyers to sellers at any given moment is determined by ""market sentiment"" and speculation.  People selling a stock think the price is going down, and people buying it think it's going up; and these beliefs are strongly influenced by news coverage and available information relating to the company.  So in the case of your company in the example that would be expected to triple in value in the next year; if everyone agreed that this was correct then the stock would triple almost instantly.  The only reason the stock doesn't reach this value instantly is that the market is split between people thinking this is going to happen and people who think it won't.   Over time, news coverage and new information will cause one side to appear more correct than the other and the balance will shift to drive the price up or down.  All this is to say that YES, large funds and their movements CAN influence a stock's trading value; BUT their movements are based upon the same news, information, analysis and sentiment as the rest of the market.  Meaning that the price of a stock is much more closely tied to news and available information than day to day trading volumes.  In short, buying good companies at good prices is just as ""good"" as it's ever been.   Also keep in mind that the fact that YOU can buy and sell stocks without having a huge impact on price is an ADVANTAGE that you have.  By slipping in or out at the right times in major market movements you can do things that a massive investment fund simply cannot." You can follow the intra-day NAV of an ETF, for instance SPY, by viewing its .IV (intra-day value) ticker which tracks it's value.   http://finance.yahoo.com/q?s=spy http://finance.yahoo.com/q?s=^SPY-IV Otherwise, each ETF provider will update their NAV after business each day on their own website. https://www.spdrs.com/product/fund.seam?ticker=spy Generally, the answer to the availability of holdings of a given mutual fund on a daily basis is no. Thus, an API is non-existent. The reasons for the lack of transparency on a daily basis is that it could/would impact the portfolio managers ability to trade. While this information would not necessarily permit individuals from front running the fund manager's trades, it does give insight in to the market outlook and strategy the fund is employing. The closest you'll be able to get to obtaining a list of holdings is by reading the most recent annual report and the quarterly filings each fund is required to file with the SEC. Two reasons why I think that's irrelevant: First, if it was on 3/31/2012 (two other sources say it was actually 4/3/2012), why the big jump two trading days later? Second, the stock popped up from $3.10 to $4.11, then over the next several trading days fell right back to $3.12. If this were about the intrinsic value of the company, I'd expect the stock to retain some value. Well on a levered fund it makes a lot of sense.  If you lose 10% on day one and you are 2x levered you just lost 20%.  Now on the next day if it corrects 10% you are still down because you've gone up 20% of a lesser amount then you went down by.  Then even worse with oil or commodity funds they are forced to roll their futures since they don't want to take delivery, which allows them to be picked off by traders.  This is referred to as levered ETF decay.  If you do trade levered funds it should be on an intraday basis, and then you're dealing with serious transaction costs. The (assets - liabilities)/#shares of a company is its book value, and that number is included in their reports. It's easy for a fund to release the net asset value on a daily basis because all of its assets (stocks, bonds, and cash) are given values every day by the market.  It's  also necessary to have a real time value for a fund as it will be bought and sold every day. A company can't really do the same thing as it will have much more diverse assets - real estate, cars, inventory, goodwill, etc.  The real time value of those assets doesn't have the same meaning as a fund; those assets are used to earn cash, while a fund's business is only to maximize its net asset value. "Prices reflect all available information. (Efficient markets hypothesis) A lot can happen between the time a stock closes on one day and opens on another. Particularly in a heavily traded stock such as IBM. Basically, you have a different ""information set"" the following day, which implies a different price. The instances where you are most likely to have a stock where the price opens at the same price is at the previous close is a thinly traded stock on which you have little information, meaning that the ""information set"" changes less from day to day." Is it correct that there is no limit on the length of the time that the company can keep the money raised from IPO of its stocks, unlike for the debt of the company where there is a limit? Yes that is correct, there is no limit. But a company can buy back its shares any time it wants. Anyone else can also buy shares on the market whenever they want.