Hi Husk,
You're not entirely correct in your assumption that one monthly transaction update might be 4 times as large as 4 weekly transactions.
Mark is correct in pointing out that while you have fewer transactions on a monthly basis they will tend to provide greater individual profits than weekly or daily trades. I can remember back in the good ole SI days the conversation drifted to which was the best day of the week and then the best hour of the day to do your trades.
Just for argument's sake let us assume a holding of 500 shares at $10 a share.
Price goes up to $12 and you sell 25 shares. The following week the price goes up to $13.50 and you sell another 23 shares. The total sale after two weeks or periods might only be42 or 43 shares at the higher price, and you will have missed out on $1.50 profit on the first 25 shares you sold. If this were to go on for an entire month or two it could amount to a significant difference in your total return.
On the buy side of things the difference is even greater. I was updating and trading weekly back before the Great Bear showed himself. Not realizing he was going to be around so long and assuming stocks would rapidly rise I continued weekly updates until I ran out of cash on many of my holdings. I did back tests on these so-called "deep divers" and discovered that in almost every case I would have been much better off had I stayed with Mr. L's recommendation of monthly updates. As Mark pointed out, not in every case, but in most cases.
There is no crystal ball to tell us which variation works for what stock during which period of time. If such a thing existed we wouldn't need AIM would we?
Bernie
Market Data 
Markets 
AI
