The Vassar Plan, although originally a moving average plan, changed so often while it was in use that it really fits in no single category, and was finally abandoned altogether. However, it was the first variable-ratio formula plan ever to receive wide publicity and is relatively simple in its principles.
The plan was conceived in 1938 at a time when investors were still mindful of the dismal market experiences of the 1929 and 1937 declines. To begin with, the plan was based on “the monthly mean price of the Dow-Jones Industrial Average for the years 1930-38,” which was 136.15.1 Therefore, 135 was taken as the median. The percentages of stocks and bonds to be held in the account were to be adjusted after each 10-point drop from this median, and after each 15-point rise.
Adjustments were made only if the market crossed an action point going away from the median, which is another way of saying that the halfway rule was to be followed: no purchases of stocks above the median, no sales below.
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