With these broad time periods set, let us now look at how the determinants of returns developed during those eras and look especially at what might h… - Burton Malkiel

Determining clear goals is a part of the investment process that too many people skip, with disastrous results. You must decide at the outset what degree of risk you are willing to assume and what kinds of investments are most suitable to your tax bracket. The securities markets are like a large restaurant with a variety of menu choices suitable for different tastes and needs. Just as there is no one food that is best for everyone, so there is no one investment that is best for all investors.

The efficient-market hypothesis does not imply, as some critics have proclaimed, that stock prices are always correct. In fact, stock prices are always wrong. What EMH implies is that no one knows for sure if stock prices are too high or too low. Nor does EMH state that stock prices move aimlessly and erratically and are insensitive to changes in fundamental information. On the contrary, the reason prices move randomly is just the opposite. The market is so efficient—prices move so quickly when information arises—that no one can buy or sell fast enough to benefit. And real news develops randomly, that is, unpredictably. It cannot be predicted by studying either past technical or fundamental information.

The castle-in-the-air theory of investing concentrates on psychic values. John Maynard Keynes, a famous economist and successful investor, enunciated the theory most lucidly in 1936. It was his opinion that professional investors prefer to devote their energies not to estimating intrinsic values, but rather to analyzing how the crowd of investors is likely to behave in the future and how during periods of optimism they tend to build their hopes into castles in the air. The successful investor tries to beat the gun by estimating what investment situations are most susceptible to public castle-building and then buying before the crowd.