Quote from xednise:
Is there any way to determine how much this has affected the volatility of an index as it relates to stop placement on a given setup? tia
Using ES as an example, if there are 100 discretionary traders using BOT assisted order entry, think of the following scenario.
1/2 of them see a buy setup at a pull back price level and then place their limit orders there. All orders will be clustered within 1 to 1.5 point range. Most order entry BOTs have options to wait 3-5 seconds and also chase the offer if it is being lifted. Some traders will setup their chase method using market orders, while some will choose to chase up to 2-3 ticks.
All these are done automatically. Bracket orders (target, trailing and stops) are placed right after the entry orders are filled, also done by the BOTs.
Think what happens when the offer is hit by a block order?
All the parked orders waiting there will fire and zoom the price level up 3 to 4 ticks, as most traders' do not like to chase the price after that. That is what we see now at critical price levels all the time - a shoot up/down of 3 to 4 ticks and come back to the same level in seconds.
Now, when the most active stocks are all traded with these BOTs, that creates a new kind of problem. The cash S&P can lift or drop 2 points in seconds due to the use of these BOTs, and that can in turn triggers other auto algorithms - like arb program, buy/sell program, etc. Thus a small push at a critical level can result in extremely fast price movement.
Knowing that, it implies no stops are safe if placed within current noise level, making the risk/reward ratio for basic daytrade setups much less attractive.
I keep track of the average 15-min bar range in the regular session as my reference for stop placement. As of today, the average stands at 9 pts. It used to be 4 or less several months ago.