Where can I find historical P/E ratios for companies?
"The mathematics site, WolframAlpha, provides such data. Here is a link to historic p/e data for Apple. You can chart other companies simply by typing ""p/e code"" into the search box.  For example, ""p/e XOM"" will give you historic p/e data for Exxon. A drop-down list box allows you to select a reporting period : 2 years, 5 years, 10 years, all data.  Below the chart you can read the minimum, maximum, and average p/e for the reporting period in addition to the dates on which the minimum and maximum were applicable."
"What you need to do is go to yahoo finance and look at different stock's P/E ratios. You'll quickly see that the stocks can be sorted by this number. It would be an interesting exercise to get an idea of why P/E isn't a fixed number, how certain industries cluster around a certain number, but even this isn't precise. But, it will give you an idea as to why your question has no answer. ""Annual earnings are $1. What is the share price?"" ""Question has no answer""" It's quite alright, it's been over a decade since he passed so I'm not particularly sensitive about it any more.  I'll have a look at investopedia, but what I'm mainly interested in is private equity. I wanted to ask directly about that, but I feel that I need a frame of reference to understand what's going on. As in, I doubt I'd be able to really get private equity without first having an understanding of public trading.  Is this subreddit really that reputable? I've learned to not really trust reddit, for the most part. Is there some kind of curation here? "Thanks for the response.   I am using WRDS database and we are currently filtering through various variables like operating income, free cash flow etc.  Main issue right now is that the database seems to only go up to 2015...is there a similar database that has 2016 info?  filtering out the ""recent equity issuance or M&amp;A activity exceeding 10% of total assets"" is another story, namely, how can I identify M&amp;A activity? I suppose we can filter it with algorithm stating if company's equity suddenly jumps 10% or more, it get's flagged" There are books on the subject of valuing stocks. P/E ratio has nothing directly to do with the value of a company. It may be an indication that the stock is undervalued or overvalued, but does not indicate the value itself. The direct value of company is what it would fetch if it was liquidated. For example, if you bought a dry cleaner and sold all of the equipment and receivables, how much would you get? To value a living company, you can treat it like a bond. For example, assume the company generates $1 million in profit every year and has a liquidation value of $2 million. Given the risk profile of the business, let's say we would like to make 8% on average per year, then the value of the business is approximately $1/0.08 + $2 = $14.5 million to us. To someone who expects to make more or less the value might be different. If the company has growth potential, you can adjust this figure by estimating the estimated income at different percentage chances of growth and decline, a growth curve so to speak. The value is then the net area under this curve.  Of course, if you do this for NYSE and most NASDAQ stocks you will find that they have a capitalization way over these amounts. That is because they are being used as a store of wealth. People are buying the stocks just as a way to store money, not necessarily make a profit. It's kind of like buying land. Even though the land may never give you a penny of profit, you know you can always sell it and get your money back. Because of this, it is difficult to value high-profile equities. You are dealing with human psychology, not pennies and dollars. "Edgar Online has this information for companies under SEC regulations and they are reported in ""Form 4"" so that should help guide your search" Your best bet is to just look at comparative balance sheets or contact the company itself. Otherwise, you will need access to a service like PrivCo to get data. You can use the Securities Exchange Commission's EDGAR search engine to search all available SEC related filings. https://www.sec.gov/edgar/searchedgar/companysearch.html Top tip: use the fast search on the right to search for the company ticker rather than by company name. Another possibly more flexible option is Yahoo finance here is an example for the dow.. http://finance.yahoo.com/q/hp?s=%5EDJI&a=9&b=1&c=1928&d=3&e=10&f=2012&g=d&z=66&y=0 Some of the individual stocks you can dl directly to a spreadsheet (not sure why this isn't offer for indexs but copy and paste should work). http://finance.yahoo.com/q/hp?s=ACTC.OB+Historical+Prices "If you are looking for numerical metrics I think the following are popular: Price/Earnings (P/E) - You mentioned this very popular one in your question.  There are different P/E ratios - forward (essentially an estimate of future earnings by management), trailing, etc..  I think of the P/E as a quick way to grade a company's income statement (i.e: How much does the stock cost verusus the amount of earnings being generated on a per share basis?). Some caution must be taken when looking at the P/E ratio.  Earnings can be ""massaged"" by the company.  Revenue can be moved between quarters, assets can be depreciated at different rates, residual value of assets can be adjusted, etc..  Knowing this, the P/E ratio alone doesn't help me determine whether or not a stock is cheap. In general, I think an affordable stock is one whose P/E is under 15. Price/Book - I look at the Price/Book as a quick way to grade a company's balance sheet.  The book value of a company is the amount of cash that would be left if everything the company owned was sold and all debts paid (i.e. the company's net worth).  The cash is then divided amoung the outstanding shares and the Price/Book can be computed.  If a company had a price/book under 1.0 then theoretically you could purchase the stock, the company could be liquidated, and you would end up with more money then what you paid for the stock. This ratio attempts to answer: ""How much does the stock cost based on the net worth of the company?"" Again, this ratio can be ""massaged"" by the company.  Asset values have to be estimated based on current market values (think about trying to determine how much a company's building is worth) unless, of course, mark-to-market is suspended.  This involves some estimating.  Again, I don't use this value alone in determing whether or not a stock is cheap. I consider a price/book value under 10 a good number.   Cash - I look at growth in the cash balance of a company as a way to grade a company's cash flow statement.  Is the cash account growing or not? As they say, ""Cash is King"".  This is one measurement that can not be ""massaged"" which is why I like it.  The P/E and Price/Book can be ""tuned"" but in the end the company cannot hide a shrinking cash balance. Return Ratios - Return on Equity is a measure of the amount of earnings being generated for a given amount of equity (ROE = earnings/(assets - liabilities)).  This attempts to measure how effective the company is at generating earnings with a given amount of equity.  There is also Return on Assets which measures earnings returns based on the company's assets. I tend to think an ROE over 15% is a good number. These measurements rely on a company accurately reporting its financial condition.  Remember, in the US companies are allowed to falsify accounting reports if approved by the government so be careful.  There are others who simply don't follow the rules and report whatever numbers they like without penalty. There are many others.  These are just a few of the more popular ones.  There are many other considerations to take into account as other posters have pointed out." The price to earnings ratio is a measure of the company's current share price compared to the annual net earnings per share.  The other way to think about this is the number of years a company would take to pay back the share price if the earnings stay constant.  This ignores factors like inflation and can be used as an indicator of risk.  During the internet bubble many companies had P/E above 24 and no possible means of earning back the share prices that were inflated largely due to speculation. Most tools like Google Finance will list the P/E for a particular quote. Dow Jones: http://en.wikipedia.org/wiki/Historical_components_of_the_Dow_Jones_Industrial_Average  NASDAQ: http://en.wikipedia.org/wiki/NASDAQ-100 (scroll down) S&P Tricky. From what I can find, you need to be in Harvard Business School, a member of CRSP, or have access to Bloomberg's databases. S&P did have the info available years ago, but no longer that I can find. James Roth provides a partial solution good for stock picking but let's speed up process a bit, already calculated historical standard deviations: Ibbotson, very good collection of research papers here, examples below Books If you're researching a publicly traded company in the USA, you can search the company filings with the SEC. Clicking 'Filings' should take you here. Your analysis is correct.  The income statement from Google states that LinkedIn made $3.4 million in 2010 - the same number you backed into by using the P/E ratio.  As you point out, the company seems overvalued compared to other mature companies.  There are companies, however, that posts losses and still trade on exchanges for years.  How should these companies be valued?  As other posters have pointed out there are many different ways to value a company.  Some investors may be speculating on substantial growth.  Others may be speculating on IPO hype. Amazon did not make a profit until 2003.  Its stock had been around for years before that and even split many times.  If you bought the stock in 1998 and still have it you would be doing quite well. 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.