# RSI - the most predictive ratio of all?

Monday, Oct 29 2012 by

Stock pickers love ratios, but which is the most predictive ratio of all? Value investors often have a bias towards low PE ratios or high dividend yields, growth investors look for high EPS growth while those that prefer a blend often lean heavily on the so-called PEG. All of these ratios have some anchoring in one of the fundamentals of the underlying business - the earnings or dividends of the company. It seems smart to ensure that you are basing investment decisions on business fundamentals but the irony is that the most predictive ratio for future price returns is completely unrelated to the underlying business. It's based entirely on the recent movements in the company's share price and has come to be known as the Relative Strength Index or RSI.

The Relative Strength Index (RSI) was first developed by J Welles Wilder in a 1978 book called New Concepts in Technical Trading Systems. It is not to be confused with the better known plain vanilla Relative Strength which simply calculates the absolute price return of a share (using the starting and end prices over a time period) and compares it to the return on the market index. RSI is a little more complicated to calculate which is perhaps why it has traditionally been used more often by technical analysts and chartists than fundamentally oriented stock pickers. We think this is a shame as recent evidence shows that it may be much more predictive than plain vanilla Relative Strength.

## How to calculate RSI

RSI uses all the price changes that occur over a given period in order to derive the average price change. Essential to the calculation is creating the ratio U/D calculated by dividing the moving average of the total price points gained on 'up' days (U) by the moving average of the total price points lost on 'down' days (D). This ratio is then 'indexed' to create a number that moves between zero and 100 as follows:

RSI = 100 - ( 100 / (1 + U/D) )

The reason technicians enjoy the RSI so much is that it can be used as an oscillator and graphically displayed underneath stock charts as depicted in the image below. Wilder believed that readings above 70 signalled an overbought stock whereas readings under 30 signalled an oversold one. RSI has generated a big following amongst day traders who use it over short time periods,…

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marben100 29th Oct '12 1 of 11

Ed,

Could you clarify, please: when you say "The top quintile of stocks based on their 28 week RSI", do you mean those with highest RSI reading (i.e. considered "overbought" in conventional T.A.) or the lowest RSI (i.e. most oversold).

Thanks,

Mark

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peterg 29th Oct '12 2 of 11

He means those with the highest RSI.

The trouble with this sort of analysis is that when you start looking into it in detail you start to find that the timespan of the RSI makes a big difference to the outcomes. Note in the article that the optimum timespan for longs and shorts differed. It's very easy to come up with spectacular returns looking at historical data - sadly carrying those returns forward is a hell of a lot harder!

Peter

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Edward Croft 29th Oct '12 3 of 11

In reply to post #68985

Hi Peter - the following is taken from the book - it clearly shows the optimum timespan.  You probably could use anywhere from 22 to 38 weeks with equivalent results.

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Edward Croft 29th Oct '12 4 of 11

In reply to post #68984

Mark - yes highest RSI reading - top quintile / top 20% of the market by RSI reading. Remember this is a longer term indicator than is usually seen on TA charts. Those kind of charts often use a 14 day RSI which is I believe more of a classic 'overbought/oversold' indicator (I should have made that clearer). This is 28 week with weekly data. It's more of an intermediate 6 month momentum indicator in this scenario.

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drainbolt 19th Sep '15 5 of 11

Edward,

In your Oct 2012 article on the predictive qualities of the RSI, you said that you would be making the 28 week and 16 week RSI available in the Stock Reports and the Screener "in the coming weeks". They do not seem to be there yet. Is it still intended to offer these indicators for screening and assessment purposes?

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mgallear 21st Sep '15 6 of 11

Does this mean that the RSI is going to be made a screenable factor in the near future?

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jimmygee 28th Sep '15 7 of 11

I too would like to know when the 16 week and 28 week RSI will be added!

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jmbobay 25th Jan 8 of 11

It seems that the RSI has not been yet added to the screener.
Will it be added in the future ?

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dfs12 25th Jan 9 of 11

I like the RSI indicator and so when this topic popped to the top of the discussion list it caught my eye. Sorry I'm being so slow but it's still not clear to me what the top quintile of RSI means. Are we saying that if we have a population of 100 stocks ordered in ascending RSI values (where the lowest RSI value is in position 1 and the highest RSI value is in position 100) then it would be those with the highest RSI values i.e. in position 81-100 that would perform the best? This would be very counter intuitive... for me high long term RSI values tend to pick out stocks that are seriously overbought. I'm not saying I'm right and this is wrong I just want to confirm things before I turn my stock selection criteria upside down!

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IGotPoesJacket 25th Jan 10 of 11

At what point do we go through the looking glass?
I'm starting to strongly suspect lots of stock behaves like Minervini and other trading systems because people (lets face it, these days it's bots) expect them to behave in a certain way and try to trade ahead of the way they're "supposed" to perform creating the pattern they were supposed to create - in other words they create self-fulfilling prophecies that those with the most powerful calculators and internet access speeds can exploit best..
I also suspect the longer the bull market goes on, the more into line these strategies fall as the ai improves, the bots take over completely. As a PI you've got no chance trying to beat supercomputers and when the inevitable crash happens, good luck in trying to get out of those companies you've bought because the chart looked good.
All in my view. Others will have a different take :)

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hari singh 3rd Feb 11 of 11

weekly rsi when builds above 65 level then watch rsi on daily chart let it go above 70 buy first dip then.stock pattern price moves sharp up when remains above 10dma and 21dma aligns above 50dma.exit on peak volume macd histo momentum above zero tapers down.Andrew Cardwell is master teacher of rsi.

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