IMO some of the 100 share trades you see are not all done to manipulate the SP. In particular, if you trade through TD Waterhouse, in order to get a transaction at $9.99 you need to have at least 30 trades in the last 3 months. Otherwise it will cost you $29 per trade or around 2% whichever is the higher. Sometimes I will buy or sell a small amount of shares just to keep my low rate, especially for when the SP gets much higher and I start taking some profits. ( at least $20 or higher) . It is not necessarily the NOT shares that I trade as I have other stocks in both my SDRSP and cash account.
In for the long haul.
Franter