Judge market efficiency from raw price action
The shortest-hand yet most reliable metric is daily volume / total shares outstanding.  A security with a high turnover rate will be more efficient than a lower one, ceteris paribus. The practical impacts are tighter spread and lower average percentage change between trades.  A security with a spread of 0% and an average change of 0% between trades is perfectly efficient.
"Assuming a price is set on an free market there are particular difficulties to pricing. A free market is one where the price is entirely determined by the willingness of people to buy and sell at a particular price point. What you perceive as price, is actually the ""tick"", i.e. the quote of the last transaction. The first and most serious major obstacle to pricing is a variation of the prisoners dilemma, a psychological phenomenon. For instance, bitcoin might be worth 4$ now, but you believe it will be worth 5$ in 3 days. Will you buy bitcoin? If acting only on your conviction, yes. But what if you consider what other people will do? Will others believe bitcoin will be worth 5$ in 3 days? Will they act on their conviction? Will the others believe that others believe that it wil be worth 5$ in 3 days, and will the others believe that the others who believe will act on their conviction? Will the others believe that others believe of still others who believe that they will act on their conviction? It goes on like this ad-infinitum. The actual behavior of any individual on the market is essentially chaotic and unpredictable (for the reason stated above and others). This is related to a phenomenon you call market efficiency. An efficient market always reflects the optimal price-point at any given time. If that is so, then you cannot win on this market, because at the time you would have to realize a competitive edge, everybody else has already acted on that information. Markets are not 100% efficient of course. But modern electronic markets can be very, very efficient (as say compared to stock markets fro 100 years ago, where you could get a competitive edge just by having access to a fast courier). What makes matters rather more difficult for price forecasting is that not only are humans engaging in the market, machines are as well. The machines may not be terribly good at what they do, but they are terribly fast. The machines that work well (i.e. don't loose much) will survive, and the ones that don't will die in short order. Since speed is one of the major benefits of the machines over humans, they tend to make markets even more efficient. Another phenomenon to price forecasting is that of information and entropy. Suppose you found a reliable method to predict a market at a given time. You act on this information and indeed you make a profit. The profit you will be able to achieve will diminish over time until it reaches zero or reverts. The reason for this is that you acted on private information, which you leaked out by engaging in a trade. The more successful you are in exploiting your forecast, the better you train every other market participant to react to their losses. Since for every trade you make successfully, there has to be somebody who lost. People or machines who lose on markets usually exit those markets in some fashion. So even if the other participants are not adjusting their behavior, your success is weeding out those with the wrong behavior. Yet another difficulty in pricing forecasts are black-swan events. Since information can have a huge impact on pricing, the sudden appearance of new information can throw a conservative forecast completely off the rails and incur huge losses (or huge unexpected benefits). You cannot quantify black-swan events in any shape or form. It is my belief that you cannot predict efficient and well working markets. You might be able to predict some very sub-optimal markets, but usually, hedge-funds are always on the hunt for inefficient markets to exploit, so by simple decree of market economics, the inefficient markets tend to be a perpetually dying species." Just to clarify things: The Net Working Capital is the funds, the capital that will finance the everyday, the short term, operations of a company like buying raw materials, paying wages erc. So, Net Working Capital doesn't have a negative impact. And you should not see the liabilities as beneficial per se. It's rather the fact that with smaller capital to finance the short term operations the company is able to make this EBIT. You can see it as the efficiency of the company, the smaller the net working capital the more efficient the company is (given the EBIT). I hope you find it helpful, it's my first amswer here. Edit: why do you say the net working capital has a negative impact? I have a buddy that used to run one of those companies that buys gold like the ones you see on TV. Here's the deal... 1) If the jewelry isn't total junk, get it appraised. Making raw materials into jewelry obviously increases the value since you can't buy jewelry for the price of raw gold. In many cases it will be worth more as jewelry, but not always. Depends on the piece. 2) Those companies generally rely on the fact that people selling jewelry to a gold dealer are in a hurry to get cash and are very negotiable on what they will take for it. Depending on how predatory they are, you will probably get between 50 and 75% of the market rate. They make a living on the spread and people's need for quick cash. They usually resell it immediately to a 3rd party that actually melts it down and resells it.  So the short answer to your question is no, you won't get close to market value with these companies. You would do better if you didn't have to go through the middle man, but then those final buyers aren't generally the ones who have set up shop to deal with the general public. Very important. Returning again to the example of the farmer, efficient, liquid markets that fairly reflect the price of a given asset allow that farmer to run his business as cost effectively as he can. That (in theory) lowers the price of his goods for the consumer. If he wasn't able to efficiently hedge, he would have to charge a premium to reflect the price risk he takes on between planting and harvesting his corn.  Being pedantic here but single stock futures markets are extremely quiet. If you were the owner of a company and you traded *options* on your company stock (a hilariously common form of insider trading) yes, that would be illegal and the SEC would certainly come after you. I don't think you're missing anything. Many modern trading systems actually warn you when trying to enter a market order, asking if you are sure that you wouldn't prefer to set a limit. I fully agree with you that it is usually just better to define a limit even 20% higher than just doing a market trade. Let me give you some examples when you still might prefer to use a market order instead of a limit: But even in those two examples a (wide) limit order might just be the safer thing to do.  So, what it really comes down to is speed: A market order has no other criterias to be defined, is thus entered faster and saves you a few seconds that might be crucial. I understand now. Thank you. How important is the existence of effective price discovery tools in a market?   And the example that you gave of a farmer is good, but when I as the owner of a company, get futures regarding, say, the stocks that I own of my company, won't that be insider trading if I do that after knowing that the value of my stocks will fall? If people assume price discovery in this case, won't they also have to assume that I am doing insider trading? Volatility is a shitty metric and is sample dependent, What is more interesting is point recurrence, i.e. how many times has a certain point been touched in x time, you can make good day trading strategies off point recurrence (relative that is). The S&P 500 is a market index.  The P/E data you're finding for the S&P 500 is data based on the constituent list of that market index and isn't necessarily the P/E ratio of a given fund, even one that aims to track the performance of the S&P 500.    I'm sure similar metrics exist for other market indexes, but unless Vanguard is publishing it's specific holdings in it's target date funds there's no market index to look at.