The firm-foundation theory argues that each investment instrument, be it a common stock or a piece of real estate, has a firm anchor of something cal… - Burton Malkiel

History, in this instance, does teach a lesson: Although the castle-in-the-air theory can well explain such speculative binges, outguessing the reactions of a fickle crowd is a most dangerous game. “In crowds it is stupidity and not mother-wit that is accumulated,” Gustave Le Bon noted in his 1895 classic on crowd psychology. It would appear that not many have read the book. Skyrocketing markets that depend on purely psychic support have invariably succumbed to the financial law of gravitation. Unsustainable prices may persist for years, but eventually they reverse themselves. Such reversals come with the suddenness of an earthquake; and the bigger the binge, the greater the resulting hangover. Few of the reckless builders of castles in the air have been nimble enough to anticipate these reversals and to escape when everything came tumbling down.

A random walk is one in which future steps or directions cannot be predicted on the basis of past history. When the term is applied to the stock market, it means that short-run changes in stock prices are unpredictable. Investment advisory services, earnings forecasts, and chart patterns are useless. On Wall Street, the term “random walk” is an obscenity. It is an epithet coined by the academic world and hurled insultingly at the professional soothsayers. Taken to its logical extreme, it means that a blindfolded monkey throwing darts at the stock listings could select a portfolio that would do as well as one selected by the experts.

A widely held belief is that the ticket to a comfortable retirement and a fat investment portfolio are instructions on what extraordinary individual stocks or mutual funds you should buy. Unfortunately, these tickets are not even worth the paper they are printed on. The harsh truth is that the most important driver in the growth of your assets is how much you save, and saving requires discipline. Without a regular savings program, it doesn’t matter if you make 5 percent, 10 percent, or even 15 percent on your investment funds. The single most important thing you can do to achieve financial security is to begin a regular savings program and to start it as early as possible. The only reliable route to a comfortable retirement is to build up a nest egg slowly and steadily. Yet few people follow this basic rule, and the savings of the typical American family are woefully inadequate.