Where did you read that? The basher handbook? Look at a newspaper from last year, and check which NYSE stocks were -20% that day, then check their status today. Stocks fluctuate all the time.
Many good stocks drop up to 20% in one day (usually it is an over-correction) from a strong growth or rally (say 200% in one to 2 days on an announcement and the settles back).
Hell, even NSDM dropped more than 20% just one month ago- Jan 6th and 7th so why didnt you get out then?
Not being critical here.. everyone has their own investment philosophy and should stick to it.. just disagree with this one.
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