Trading Strategy: Moving Average Mean Reversion

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Hi All,

I'd like to share with you a simple mean reversion technique that relies on moving averages. In short, the idea is that the mean-reversion signals can be approximated by intersections of different-length moving averages. This is best made clear by the following illustration:

http://i.imgur.com/5oi3yao.png

In which the data is from a 3,000-day dataset of a stock's closing price. In this model, we generally have one "long" moving average and one "short" moving average (in this case, 90 and 30 days, respectively). We trade when these lines intersect, then choosing to buy or sell based on the direction of the trend (whether the short MA is rising or falling). I note that we don't trade exactly when the lines intersect, but rather when they are sufficiently close (by some user-defined metric). While this is not as statistically strong as mean reversion could be, it's a reasonable approximation with plenty of nice properties because of the lag between the two MAs: a reasonable buy/sell strategy with clear signals that translates into having an effective stop-loss from any peak, except for cases of sudden and severe price crashes.

I've attached a backtest that I ran on some tech stocks between 2008 and 2010, with MA periods of 30 and 10 days.

I'm somewhat new to Quantopian and I didn't have much time to write my algorithm, so I apologize for some of the crude techniques I used in my code, which I intend to fix in future versions. I plan to rewrite the part that decides how much to invest (it's currently mostly hand-tuned with guesstimates), to add a more sophisticated stop-loss, and and to improve the heuristic for determining whether a security is trending negatively or positively. I also need to make my algorithm start shorting stocks. There's generally a great deal of calibration to be done to this algorithm. It would also probably be useful to develop some analyses that determine the best MA periods to use.

Feel free to play around with this algorithm and see if you find anything interesting!

9 responses

Nathan Goings

Pardon the bump, but this is a notebook I made to help visualize like your photo. The variables are accessible as well.

Lotanna Ezenwa

Hi John,

I spent some time looking over this over, and I have to give it to you: this is a very well calculated and intuitive algorithm.
I was able to make some pretty good improvements to the algorithm's readability and performance.

As far as lines of code goes, I sought out to make some readability improvements by streamlining some of the more rigorous methods using Quantopian builtins. I removed the need for a price database and a 30-day waiting period using the history function. I also used the records as Darrell suggested to track the positions and leverage. In order to ensure the orders went in correctly, I changed those to orders by percentages. After that, I noticed that you had placed a "pass" statement where the algorithm called for a "continue" statement. Without your comments, I definitely would have missed it.

In terms of algorithm logic, I reversed the buy/sell initiations to activate when the price over the last 4 days increases/decreases in order to ride the mean reversion momentum up as opposed to guessing whether it will or not. As an aside, this makes the algorithm more of a hybrid than mean reverting, but I was able to gain some get some good improvements to the sharpe ratio. I also removed a security in your sample that was delisted in 2010 to view the algorithm's performance to date. It performs very well, great job.

Best,
Lotanna Ezenwa

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Simon Thornington

It would be helpful to see if this is still profitable without the hand-picked stocks, but rather using some sort of dynamic universe.

Lotanna Ezenwa

Yeah, I'm currently working on editing the logic to encompass some other stocks using pipeline. I tried putting a few in there at random and the performance was lacking.

My hypothesis at the moment is that new securities selected based on fundamentals will do just as well. I'll post the update when I finish.

Disclaimer

Luca

Same algorithm on a universe of 600 stocks. It might be worth double checking I didn't introduce any bug.

Luca

and on a universe of 50 stocks

Elsid Aliaj

How about testing it with a 3X ETF

Tony Chang

if 10day.mean > 30day.mean, we long (buy). If 10day.mean < 30day.mean, shall we short-sell ?

Viridian Hawk

@Tory, It's a little bit more involved. It looks for whether the 10day mean is greater than 95% of the 30day mean. What the algo is trying to compensate for is that moving averages are a lagging indicator, so it's fudging the signals so that they trip earlier. It also checks for a 3-day continuous uptrend as a confirmation signal. And visa versa for selling. Also has a 8% stop loss. It all sounds good in theory, but as Luca's posts pointed out, it's not the algorithm that produces those impressive results in the initial backtests -- it was the bias introduced by the hand-selected stocks.

The difficulty with crossovers is that 1. due to the smoothing they're a lagging indicator, and 2. the frequency and amplitude of the price waveform is too variable for fixed-period crossovers to discern between signal and noise -- they don't do a good job of detecting whether a recent price move is establishing new momentum as opposed to a temporary move that will quickly revert. So just as often as not by the time the signal gets triggered the price is already moving in the other direction.

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