Separating Prediction From Fact

We are told time and time again that you can’t predict the market. And time and time again people try to predict the market. Many model the market using stochastic principles, and use it to predict the market. I find this completely amusing (stochastics is about multiple destinys based on a single context.)

TraderFeed a favorite blog of mine had the following to say (Are We Making a Bottom).

There is both the sense that we could go much lower in a washout (a “Black Monday” scenario) and that we could be seeing an important bottom in the making.

Fair enough, good point we might be at an inflection point.


To give a bit of perspective on this one-sidedness, we’ve only had 75 other occasions since 1960 (!) in which 70% or more of the volume has been in declining stocks over a two-week interval. That is out of almost 12,000 trading days. Stated otherwise, the current market is in the top 1% of all market occasions since 1960 for bearish concentration of volume.

This is where I say, so what! That was then and this is now. In fact if I thought about this completely I would say, “stay out of the market…” Though his statistics seem to say the following:

If we look across all 75 instances, the market was up 41 times and down 34 after a five day period for an average gain of .87%. When we look three weeks out, however, the market was up only 36 times and down 39 times, for a subnormal gain of only .08%.

This statistic tells me that we are in a crap shot and it could go either way. When you are up almost as many times as you are down I get the feeling that whatever you do will be both right and wrong. You could play this market by creating a straddle, but with an average gain of 0.87% I would be tempted to believe that you could not get the option premium paid for.

In the end TraderFeed says the following:

That tells me that the current weakness offers risk as well as reward for shorter timeframe traders, but also is a heads up for investors seeking value.

Which reminds me of a horoscope… Worded in such a way that everybody sees something they want. Look I am not harping on TraderFeed. In fact I think TraderFeed is very diplomatically saying, “Beats the crap out of me of what the market will do next.”

TraderFeed is not the only one trying to make predictions. Neural Market Trends referenced an article on Ugly, which referenced an article on New Scientist. You should read what each party has to say on the topic and you will see that each has their own take on the same topic matter.

What I see is an attempt to use AI to make predictions or find patterns, where as I have written before none exist. But wait, I want to prove to you that you can’t make predictions EVEN if you have 100% solid evidence of where to make trades.

Consider the following image:

This is my profit level for an average day of the algorithmic trading system doing its thing. On this day I happened to make a daily profit of 0.85%. I have days where I do much better, and much worse. As I wrote, this is an average day.

Look at the signals that indicate whether I should buy or sell.

When the signals are above I buy, below I sell. Now compare the profitability of my trading system, and the signals. Notice a pattern? The pattern, and it is a solid visual pattern, if the two signals diverge stop trading! Whenever my profitability drops notice how the signals diverge. Its not only like this once or twice, but whenever the signals diverge STOP trading!

From a visual perspective it should be pretty easy to spot this pattern and stop trading, right? WRONG! I have tried many statistical analysis (eg T-Test, F-Test, etc, etc) and they prove nothing. My signals end up looking like the following images:

All of the filters and statistics when applied result in me making quite a bit less money than taking my lumps. So why if my pattern is 100% rock solid and apparent can I make my trading system not be more profitable?

The answer is that you cannot predict the market!

When I presented my graphs to a person who studied statistics he had the following to say.

Statistics are great for knowing what has happened in the past. For example you can ask, “how many kids fell down the stairs in the past year.” But they are horrible at predicting the future. Statistics cannot be used to tell you what the problem with the stairs are, and it cannot predict how many kids will fall down the stairs. It could happen that you do nothing and less kids fall. Statistics will tell you something changed and that now less kids are falling down stairs.

When I look at your graphs I think that you can’t automate it and will have to rely on visual means.

What he was saying is that by applying statistics to predict, the noise of the data will get in the way of figuring out what is relevant and not relevant. The filtered signals are not wrong, but are being influenced by data that does not interest you. I could filter out the noise, but then I do what you should not do, which is over-fit the data to create the required signals. The problem is what is relevant data and what is noise?

Does this mean I need to take my lumps? Yeah it does…

Hello There Mr Roboto!
(the song and era says it all... http://www.devspace.com)

Monday, Jul. 30, 2007 by Christian

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  • 1. Phil  |  July 30th, 2007 at 9:12 pm

    Past performance is not an indicator of future results?

    ;)

    Have to say I am impressed that you made 0.85% though - you only need a few of those days a year and you will be retired soon enough.

    Have you been trading for a full year yet? What is your annualised figure? How does the system hold up over the longer term?

    Cheers,

    Phil

  • 2. Christian Gross  |  July 31st, 2007 at 4:00 am

    I am not trading now, but traded live from beginning of June to middle of July. During that time my system had 71.75% returns calculated per anum, which is a bit higher than I expected. Doing some conservative numbers I expect in the long term 30-50% annualized returns. My statistics said 66%, but I don’t completely trust the statistics due to execution strategies.

    I am not trading right now because I don’t trust my system to trade completely on its own. I also have other things to do, like get my book done. When I was trading I was watching the system like a hawk to make sure that I would not have my account cleaned out or have the system hang at the wrong time. Right now I am optimizing strategies and optimizing the application.

    Of course people talk about pullbacks and such. I can’t 100% say that it will not happen. But what says to me that I don’t think it will happen is because the model and real life are reasonable. My model accounts for slippage, execution costs, etc, etc. It took me quite a bit of time to figure out correct model costs.

    Though I have learned several things:

    1) You need two strategies: market and execution. Most trading software and people focus on market strategies. And I have learned that market strategies will cause you to loose money if improperly implemented. Execution strategies are strategies where once you figured out the market, what do you do? People often forget about execution strategies and consider it as part of the market strategy.

    2) Anybody who sells trading systems is selling you snake oil. If the trading system or software does so well why are they not using it themselves? The market is the only place where you don’t need to sell shovels to make money. If you have developed the magic shovel then you can make more money using that magic shovel than selling it to somebody.

    3) Whenever you create a strategy you need to include the costs of the market. I found that by not including the costs of the market you will find a trading strategy that is not profitable. The thinking that you want to find the most profitable trading strategy and then take lumps in real life is misguided. I found that the market is not about factoring in costs, but having your simulation as close as possible to real life. Once I figured out a trading strategy with no costs, and one with costs. They were two completely different strategies that had nothing in common.

    Am I happy? Yeah. Am I nervous as heck? Damm straight because as much as it seems to be working I have to keep pinching myself that it is real. I am right now nervous as heck because I keep getting the feeling, “Haha gotcha ya fooled ya!”

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