Sam..

I am going to rephase this because it is not allways true..

The price drops as soon as a short sale occurs..as stock price falls on a sell function..

Shorting is a risky business and the share price does not allways go down..the way you want it to go when you short...it can go up...and you can loose your hiney..and have to buy back your borrowed shorted stocks higher than you borrowed and SOLD them at..

Reading through that link and all the components of shoprt selling can explain the phenomonae much better than I can..especially when I'm crawling around on the floor in Vegas..