Greetings -- Sohamdas wrote: "Dr Bandy, what you said is true, about the second alternative. The risk conditions are violated, with further scale-ins,when we double up etc.
But consider, if with each scale-in, we also move the stop loss point.In that scenario, the situation can morph into one, where the risk doesnt increase linearly with position,it increases slower than the growth of positions." ------------------- I agree that the risk calculations change as the price moves in the direction that gives profit. But in order to keep to the original risk profile, the amount of the scale in is limited to the amount of the gain. That is, before scaling in, recalculate the position size permitted and scale in by that amount. The amount of additional position size allowed is usually much less than the original position was. My argument against scaling in is with schemes that take a full position at entry, then add an amount that is large relative to the initial position (100%, 50%, 33%, or 25% are typical). Unless the open profit supports the new position size of 200%, 150%, etc, the risk is now higher than originally permitted. It is OK to do this if you realize that by doing so you are using aggressive position sizing and have worked through the consequences. The original position could be taken at a position size that anticipates all of the scale in trades will be taken. This assures that risk will remain limited. But for those trades when the conditions necessary to add a scale in position do not occur, only a portion of the funds have been committed to the trade and the profit is less than it would have been if a full position was taken at the original signal. I think it is better to treat each signal -- the original and each scale in -- as a unique trading system. Work through the design, testing, and validation of each separately, then apply position sizing to each and to the portfolio that results from trading all of them. Be aware that all of these systems will be trading the same data series in the same direction, and an adverse price move will effect them all the same, increasing the risk rather than diversifying it. Think about it this way -- You have a profitable system with logic that gives you good entry signals. If you wait until the trade shows a profit to add to the position, you forfeit the profit from the funds that were not used at the initial signal. If the scale in portion gives better results than the original signal, then the entry logic needs to be revised. ------------ The same situation occurs at scale out. A commonly described technique is to take partial profits and reset the stop when some condition is met. In almost all of the tests I have run using this technique, the performance of the system over a period of many trades is poorer than if the entire position is held until the final exit signal. Think about it this way -- You have a profitable system. If you reduce your position size when trades have some profit and, on average, the trades go on to be more profitable, you forfeit some of the potential profit. If you reduce your position size when trades have some profit and, on average, the trades go on to become losers, your exit logic needs to be revised. Thanks, Howard
