Quote from doublea:
Many traders and gurus think that the 200 dma works as a major support or a resistance. So say price is above the 200 dma and someone who is short will look for an opportunity to take profits near the 200 dma, on the other hand there are other people who want to initiate long positions near the 200 dma. This combination will eventually end up supporting the price at/near the 200dma at least for the short term. This is how TA works. It is a self fulfilling prophecy, nothing else.
TA is like a broken clock. Even a broken clock tells the accurate time twice a day.
I've heard this said before and wondered if it were true. Here's another reason I have to possibly doubt it:
Using EnsignSoftware, I have the capability to use a random-generated data feed to test strategies on. The concept is that it would closely mimic market behavior enough to be useful outside of market hours or in the absence of actual price data to practice with.
While I felt that the random-generated feed was smoother than the time frame I personally trade with eur/usd, it did essentially behave similarly to the live price action I see during busy market hours. I also think there were differences due to the 24 hour nature of forex, which leads to different levels of volatility throughout each 24 hours in a way that is different from what one sees on stocks or indexes between opening and closing bells.
That said, my observation led me to consider that rather than TA being a self-fulfilling prophecy, it is simply good at at forecasting price behavior which is essentially random. Perhaps the main differences we see wherein one instrument will find support at a 200ema and another at 150ema has more to do with volatility and volume than traders enmasse reacting to a certain level.
Again, THAT said, I have read studies that deal with the cascading stoploss phenomenon, which at times leads to very quick large scale moves in forex, that indicate a force in operation beyond random price behavior.
Perhaps it's most accurate to conclude that TA operates in response to randomness in faster time frames, and in response to the behavior of traders on a large scale during major market moving events.
Even then it's interesting how one is able to go out to slower time frames and see that price behavior smoothed into a pattern than once again resembels a random-generated data feed.
Kali