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
Market capitalization is one way to represent the value of the company. So if a company has 10 million shares, which are each worth $100, then the company's market capitalization is 1 billion. Large cap companies tend to be larger and more stable. Small cap companies are smaller, which indicates higher volatility. So if you want more aggressive investments then you may want to invest in small cap companies while if you lean on the side of caution then big cap companies may be your friend. "It looks like these types of companies have to disclose the health of their accounts to CFTC (Commodity Futures Trading Commission). That is the gist I get at least from this article about the traders that lost money due to the Swiss removing the franc’s cap against the euro. The article says about the U.S. retail FOREX brokerage: Most of FXCM’s retail clients lost money in 2014, according to the company’s disclosures mandated by the CFTC. The percentage of losing accounts climbed from 67 percent in the first and second quarters to 68 percent in the third quarter and 70 percent in the fourth quarter. Side note: The Swiss National Bank abandoned the cap on the currency's value against the euro in mid-January 2015. But above paragraph provides data on FXCM’s retail clients in 2014. It could consequently be concluded that, even without ""freak events"" (such as Switzerland removing the franc cap), it is more likely for an investor to NOT make a profit on the FOREX market. This is also in line with what ""sdfasdf"" and ""Dario Fumagalli"" say in their answers." Google Finance and Yahoo Finance have been transitioning their API (data interface) over the last 3 months. They are currently unreliable. If you're just interested in historical price data, I would recommend either Quandl or Tiingo (I am not affiliated with either, but I use them as data sources). Both have the same historical data (open, close, high, low, dividends, etc.) on a daily closing for thousands of Ticker symbols. Each service requires you to register and get a unique token. For basic historical data, there is no charge. I've been using both for many months and the data quality has been excellent and API (at least for python) is very easy! If you have an inclination for python software development, you can read about the drama with Google and Yahoo finance at the pandas-datareader group at https://github.com/pydata/pandas-datareader. "The professional financial advisors do have tools which will take a general description of a portfolio and run monte-carlo simulations based on the stock market's historical behavior. After about 100 simulation passes they can give a statistical statement about the probable returns, the risk involved in that strategy, and their confidence in these numbers.  Note that they do not just use the historical data or individual stocks. There's no way to guarantee that the same historical accidents would have occurred that made one company more successful than another, or that they will again. ""Past performance is no guarantee of future results""... but general trends and patterns can be roughly modelled. Which makes that a good fit for those of us buying index funds, less good for those who want to play at a greater level of detail in the hope of doing better. But that's sorta the point; to beat market rate of return with the same kind of statistical confidence takes a lot more work." You're only counting one year.   Let's say 30 years of data, minutewise, for 2,000 stocks, and 50 characters per data line. That's 1.5TB of data.  Since the market has grown, that's an overestimate - 30 years ago there weren't 2,000 stocks in the NYSE - but it still gives us ballpark of roughly 1 TB.  Not an easy download. The value premium would state the opposite in fact if one looks at the work of Fama and French. The Investment Entertainment Pricing Theory (INEPT) shows a graph with the rates on small-cap/large-cap and growth/value combinations that may be of interest as well for another article noting the same research. Index fund advisors in Figure 9-1 shows various historical returns up to 2012 that may also be useful here for those wanting more detailed data. How to Beat the Benchmark is from 1998 that could be interesting to read about index funds and beating the index in a simpler way. "Often you are right, and the current information is ""priced in"", but I would say in times of market boom like this that the market can definitely overprice. Price is driven by trades/last trade. Someone may be willing to pay X, and do so, making the price now X, but that does not mean it is worth X. You could very well be paying a premium for it's perceived desirability. This is why investors/analysts spend time and energy on valuations, they want to compare the markets current price to what the price theoretically should/would be if it were purely driven by the data, in effect trying to remove sentiment from the equation to gain a more realistic idea of what a company is worth.  Side note adding on that, don't mistake this as saying one should pay a lot of attention to analysts or their price targets, though analysts do have insightful things to say." Market capitalization is one way to represent the value of the company. So if a company has 10 million shares, which are each worth $100, then the company's market capitalization is 1 billion. Large cap companies tend to be larger and more stable. Small cap companies are smaller, which indicates higher volatility. So if you want more aggressive investments then you may want to invest in small cap companies while if you lean on the side of caution then big cap companies may be your friend.