Share Price Determination

At any given moment, an equity's price is strictly a result of supply and demand. The supply is the number of shares offered for sale at any one moment. The demand is the number of shares investors wish to buy at exactly that same time. The price of the stock moves in order to achieve and maintain equilibrium.

When prospective buyers outnumber sellers, the price rises. Eventually, sellers attracted to the high selling price enter the market and/or buyers leave, achieving equilibrium between buyers and sellers. When sellers outnumber buyers, the price falls. Eventually buyers enter and/or sellers leave, again achieving equilibrium.

Thus, the value of a share of a company at any given moment is determined by all investors voting with their money. If more investors want a stock and are willing to pay more, the price will go up. If more investors are selling a stock and there aren't enough buyers, the price will go down.

*Note: "For Nasdaq-listed stocks, the price quote includes information on the bid and ask prices for the stock."

Of course, that does not explain how people decide the maximum price at which they are willing to buy or the minimum at which they are willing to sell. In professional investment circles the efficient market hypothesis (EMH) continues to be popular, although this theory is widely discredited in academic and professional circles. Briefly, EMH says that investing is overall (weighted by a Stdev) rational; that the price of a stock at any given moment represents a rational evaluation of the known information that might bear on the future value of the company; and that share prices of equities are priced efficiently, which is to say that they represent accurately the expected value of the stock, as best it can be known at a given moment. In other words, prices are the result of discounting expected future cash flows.

The EMH model, if true, has at least two interesting consequences. First, because financial risk is presumed to require at least a small premium on expected value, the return on equity can be expected to be slightly greater than that available from non-equity investments: if not, the same rational calculations would lead equity investors to shift to these safer non-equity investments that could be expected to give the same or better return at lower risk. Second, because the price of a share at every given moment is an "efficient" reflection of expected value, then—relative to the curve of expected return—prices will tend to follow a random walk, determined by the emergence of information (randomly) over time. Professional equity investors therefore immerse themselves in the flow of fundamental information, seeking to gain an advantage over their competitors (mainly other professional investors) by more intelligently interpreting the emerging flow of information (news).

The EMH model does not seem to give a complete description of the process of equity price determination. For example, stock markets are more volatile than EMH would imply. In recent years it has come to be accepted that the share markets are not perfectly efficient, perhaps especially in emerging markets or other markets that are not dominated by well-informed professional investors.

Another theory of share price determination comes from the field of Behavioral Finance. According to Behavioral Finance, humans often make irrational decisions—particularly, related to the buying and selling of securities—based upon fears and misperceptions of outcomes. The irrational trading of securities can often create securities prices which vary from rational, fundamental price valuations. For instance, during the technology bubble of the late 1990s (which was followed by the dot-com bust of 2000-2002), technology companies were often bid beyond any rational fundamental value because of what is commonly known as the "greater fool theory". The "greater fool theory" holds that, because the predominant method of realizing returns in equity is from the sale to another investor, one should select securities that they believe that someone else will value at a higher level at some point in the future, without regard to the basis for that other party's willingness to pay a higher price.

Thus, even a rational investor may bank on others' irrationality.

Share Price Determination Topic - Short Selling

In finance, short selling (also known as shorting or going short) is the practice of selling assets, usually securities, that have been borrowed from a third party (usually a broker) with the intention of buying identical assets back at a later date to return to the lender.