Highest market cap for a company from historical data
In common with many companies, Microsoft has been engaging in share buyback programmes, where it buys its own shares in the market and then cancels them. It's often a more tax-efficient way to distribute profits to the shareholders than paying a dividend. So there were more Microsoft shares in circulation in 1999 than there are now. See here for information. Adjustments can be for splits as well as for dividends.  From Investopedia.com: Historical prices stored on some public websites, such as Yahoo!   Finance, also adjust the past prices of the stock downward by the   dividend amount. Thus, that could also be a possible factor in looking at the old prices. Everything would depend on whether the calculation is being done using the company's all-time high intraday trading price or all-time high closing price. Further, I've seen calculations using non-public pricing data, such as bid-offer numbers from market makers, although this wouldn't be kosher. The likelihood is that you're seeing numbers that were calculated using different points in time. For the record, I think Apple has overtaken Microsoft's all-time highest market cap with a figure somewhere north of $700 billion (nominal).  Here's an interesting article link on the subject of highest-ever valuations: comparison of highest market caps ever
"Matt explains the study numbers in his answer, but those are the valuation of the brand, not the value of the company or how ""rich"" the company is.   Presuming that you're asking the value of the company, the usual way for a publicly traded company to be valued is by the market capitalization (1).  Market capitalization is a fairly simple measure, basically the total value of all the shares of stock in that company. You can find the market cap for any publicly traded company on any of the usual finance sites like Google Finance or Yahoo Finance. If by rich you mean the total value of assets (assets being all property, including cash, real property, equipment, and licenses) a company owns, that information is included in a publicly traded company's quarterly SEC filing and investor releases, but isn't usually listed on the popular finance sites. An example can be seen at Duke Energy's Investor Relation Site (the same information can be found for all companies on EDGAR, the SEC's search tool).  If you open the most recent 8-K (quarterly filing), and go to page 8, you can see that they have $33B+ in assets, and a high level breakdown of those. Note that the numbers are given in millions of dollars For a privately held company this information may or may not be available and you'd have to track it down if it is available. I picked Duke Energy because it's the first thing that popped into my mind.  I have no affiliation with Duke, and I don't directly own any of their stock." Willis Group Holdings Set to Join the S&P 500; Fossil Group to Join S&P MidCap 400; Adeptus Health to Join S&P SmallCap 600 notes in part for the S & P case: Willis Group Holdings plc (NYSE:WSH) will replace Fossil Group Inc.   (NASD:FOSL) in the S&P 500, and Fossil Group will replace Towers   Watson & Co. (NASD:TW) in the S&P MidCap 400 after the close of   trading on Monday, January 4. Willis Group is merging with Towers   Watson in a deal expected to be completed on or about that date   pending final conditions. Post merger, Willis Group Holdings will   change its name to Willis Towers Watson plc and trade under the ticker   symbol “WLTW”. Fossil has a market capitalization that is more   representative of the midcap market space. As of Jan. 8, Fossil is about $1.44B in market cap and Willis is $21.02B for those wondering. Apple with a market cap of $540.58B is 3.26% of the index making the entire index worth approximately $16,582.21B, so Fossil is worth .00868% of the overall index for those wanting some numbers here. Thus, if a company acquires another and becomes bigger than there can be replacements made in those indices that have an artificial number of small members. Alternatively, a member may be removed for lack of representation where it is just so small compared to other companies that may be a better fit as some indices could be viewed as actively managed in a sense. In contrast, there are indices like those from Russell, known for the Russell 2000 small-cap index: Q: Why don't you reconstitute the indexes more often than once a year? A: Maintaining representative indexes must be weighed against the   costs associated with making frequent changes to index constituents   (namely, buying and selling stocks). The Russell Indexes are annually reconstituted because our research   has shown that this strikes a reasonable balance between accuracy and   cost. We originally reconstituted our indexes quarterly, then   semi-annually, but found these options to be suboptimal. Our extensive   research demonstrates that annual reconstitution accurately represents   the capitalization segments and minimizes the turnover required to   reflect the segments as they change. Thus there can be different scenarios.  Then there can be the effect on index funds when price-weighted indices like the Dow Jones Industrial Average has a member that does a stock split that causes some rebalancing too. On the DJIA Divisor: The Dow Jones Industrial Average (DJIA) is a price-weighted index that   is calculated by dividing the sum of the prices of the 30 component   stocks (Dow Jones Industrial Average components) by a number called   the DJIA Divisor or Dow Divisor . The index divisor is updated   periodically and adjusted to offset the effect of stock splits, bonus   issues or any change in the component stocks included in the DJIA.   This is done in order to keep the index value consistent. As per the chart pattern when ever a stock breaks its 52 week high. This information may differ for penny stocks,small caps and mid cap stocks Market cap should be share price times number of shares, right? That's several orders of magnitude right there... Market Capitalization is the equity value of a company. It measures the total value of the shares available for trade in public markets if they were immediately sold at the last traded market price. Some people think it is a measure of a company's net worth, but it can be a misleading for a number of reasons. Share price will be biased toward recent earnings and the Earnings Per Share (EPS) metric. The most recent market price only reflects the lowest price one market participant is willing to sell for and the highest price another market participant is willing to buy for, though in a liquid market it does generally reflect the current consensus. In an imperfect market (for example with a large institutional purchase or sale) prices can diverge widely from the consensus price and when multiplied by outstanding shares, can show a very distorted market capitalization. It is also a misleading number when comparing two companies' market capitalization because while some companies raise the money they need by selling shares on the markets, others might prefer debt financing from private lenders or sell bonds on the market, or some other capital structure. Some companies sell preferred shares or non-voting shares along with the traditional shares that exist. All of these factors have to be considered when valuing a company. Large-cap companies tend to have lower but more stable growth than small cap companies which are still expanding into new markets because of their smaller size. Yahoo provides dividend data from their Historical Prices section, and selecting Dividends Only, along with the dates you wish to return data for. Here is an example of BHP's dividends dating back to 1998. Further, you can download directly to *.csv format if you wish: http://real-chart.finance.yahoo.com/table.csv?s=BHP.AX&a=00&b=29&c=1988&d=06&e=6&f=2015&g=v&ignore=.csv Are you implying that Amazon is a better investment than GE because Amazon's P/E is 175 while GE's is only 27?  Or that GE is a better investment than Apple because Apple's P/E is just 13.  There are a lot of other ratios to consider than P/E.  I personally view high P/E numbers as a red flag.  One way to think of a P/E ratio is the number of years it's expected for the company to earn its market cap.  (Share price divided by annual earnings per share)  It will take Amazon 175 years to earn $353 billion. If I was going to buy a dry cleaners, I would not pay the owner 175 years of earnings to take control of it, I'd never see my investment back. To your point.  There is so much future growth seemingly built in to today's stock market that even when a company posts higher than expected earnings, the company's stock may take a hit because maybe future prospects are a little less bright than everyone thought yesterday. The point of fundamental analysis is that you want to look at a company's management style and financial strategies.  How is it paying its debt?  How is it accumulating the debt?  How is it's return on assets?  How is the return on assets trending?  This way when you look at a few companies in the same market segment you may have a better shot at picking the winner over time.  The company that piles on new debt for every new project is likely to continue that path in to oblivion, regardless of the P/E ratio. (or some other equally less forward thinking management practice that you uncover in your fundamental analysis efforts). And I'll add... No amount of historical good decision making from a company's management can prepare for a total market downturn, or lack of investor confidence in general.  The market is the market; sometimes it's up irrationally, sometimes it's down irrationally. I haven't seen one of these in quite some time. Back in the 1970s, maybe the 1980s, stock brokers would occasionally send their retail clients a complimentary copy once in a while. Also, I remember the local newspaper would offer a year-end edition for a few dollars (maybe $3) and that edition would include the newspaper company's name on the cover. They were very handy little guides measuring 5 1/2 x 8 (horizontal) with one line devoted to each company. They listed hundreds of publicly traded companies and had basic info on each company. As you stated, for further info you needed to go to the library and follow-up with the big S&P and/or Moody's manuals. That was long before the internet made such info available at the click of a button on a home computer! I am looking at size by revenue.  Looking at market capitalization gives a much different list.  I don't think market cap is a good metric for this discussion.  According to market cap Telsa is the largest automotive company in the US, but that is because it is expected to do well in the future by the investment community.  According to market cap what is reddit worth? Go to http://finance.google.com, search for the stock you want. When you are seeing the stock information, in the top left corner there's a link that says 'Historical prices'. Click on it. then select the date range, click update (don't forget this) and 'Download to spreadsheet' (on the right, below the chart). For example, this link takes you to the historical data for MSFT for the last 10 years. http://finance.yahoo.com has something similar, like this. In this case the link to download a CSV is at the bottom of the table. "You are comparing ""market caps"" and ""enterprise value"".  If the company has four billion dollars cash in the bank, then the value would be four billion plus whatever the business itself is worth as a business. If the business itself is only worth 400 million, then you would have 4.4bn market caps and 400 million enterprise value. The ""enterprise value"" is basically how much the business would be worth if it had no cash or no debt.  These numbers would be a very unusual situation. It could happen for example if a big company has sold 90% of its business for cash. When you buy a share of the company, you get a tiny share of the business and you own a tiny share of the cash. This stock will very likely keep its value, but won't make much money.  On the other hand, more common would be a company where the business is worth 4bn, but the company has also 4bn debt. So it is worth exactly zero. Market caps close to zero, but enterprise value $4bn, because you ignore the debt in the enterprise value.  Edit: Sorry, got the ""enterprise value"" totally wrong, read millions instead of billions: Your numbers would mean that you have a huge, huge company with close to 440bn debt. Most likely someone made a mistake here. A ""normal"" situation would be say a company with a business that is worth $500 million, but they have $100 million debt, so market caps = $400 million but enterprise value = $500 million.  PS. Yahoo has the same nonsense numbers on their UK site, and for other companies (I just checked Marks and Spencer's which apparently has an enterprise value of 800 billion pound with a totally ridiculous P/E ratio." You need a source of delisted historical data.  Such data is typically only available from paid sources. According to my records 20 Feb 2006 was not a trading day - it was Preisdent's Day and the US exchanges were closed. The prior trading date to this was 17 Feb 2006 where the stock had the following data: Open: 14.40 High 14.46 Low 14.16 Close 14.32 Volume 1339800 (consolidated volume) Source: Symbol NVE-201312 within Premium Data US delisted stocks historical data set available from http://www.premiumdata.net/products/premiumdata/ushistorical.php Disclosure: I am a co-owner of Norgate / Premium Data. The difference between the two numbers is that the market size of a particular product is expressed as an annual number ($10 million per year, in your example).  The market cap of a stock, on the other hand, is a long-term valuation of the company. Check out WorldCap.org. They provide fundamental data for Hong Kong stocks in combination with an iPad app. Disclosure: I am affiliated with WorldCap. I couldn't find historical data either, so I contacted Vanguard Canada and Barclays; Vanguard replied that  This index was developed for Vanguard, and thus historical information is available as of the inception of the fund. Unfortunately, that means that the only existing data on historical returns are in the link in your question. Vanguard also sent me a link to the methodology Barclay's uses when constructing this index, which you might find interesting as well.  I haven't heard from Barclays, but I presume the story is the same; even if they've been collecting data on Canadian bonds since before the inception of this index, they probably didn't aggregate it into an index before their contract with Vanguard (and if they did, it might be proprietary and not available free of charge).