A characteristic of a healthy bull market is that it
makes higher-highs and higher-lows. This indicates a continual upward
shift in expectations and the supply/demand lines. The amount that
prices retreat following a higher-high can be measured using a technique
referred to as "percent retracement." This measures the percentage that
prices "retraced" from the high to the low.
For example, if a stock moves from a low of 50 to a
high of 100 and then retraces to 75, the move from 100 to 75 (25 points)
retraced 50% of the original move from 50 to 100.
Interpretation
Measuring the percent retracement can be helpful
when determining the price levels at which prices will reverse and
continue upward. During a vigorous bull market, prices often retrace up
to 33% of the original move. It is not uncommon for prices to retrace up
to 50%. Retracements of more than 66% almost always signify an end to
the bull market.
Some investors feel that the similarities between
33%, 50%, and 66% and the Fibonacci numbers of 38.2%, 50%, and 61.8% are
significant. These investors will use Fibonacci Levels to view
retracement levels.
Example
I labeled the following chart of Great Western at
three points (labeled "A," "B," and "C").
These points define the price before the price move
("A"), at the end of the price move ("B"), and at the retraced price
("C"). In this example, prices have retraced 61.5% of the original price
move.