Rules of thumb have existed in investing ever since people looked for patterns in stock price movements. Market timing was the goal, of course, along with a shortcut to quicker wealth. And it didn’t take much to find one. A limited experience, maybe a modicum of study, could unearth a market timing rule.
The first half of the 1900s had its rules of thumb that worked for a while. Charles Amos Dice wrote about the more popular rules in the decades leading up to 1929:
In the first place, there was the conviction that whatever goes up must sooner or later come down. This seeming truism carried tucked safely away the implication that the distance of the fall would approximate the number of points gained in the preceding rise. Furthermore, it implied that the major advances and declines followed one another in more or less regular recurrence…
In the second place, it was a common prewar and also post war belief that the market might reasonably be expected to be at the end of a major advance after 20 to 24 months of consistent climbing. Even as late as 1923, the old yardstick did not fail the trader… Furthermore, major declines might well be expected to run their course in about 11 to 15 months. Before the trajedy of 1920, there was but one exception to this almost mechanical rule since 1903…
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