There are many ways to trade pairs, but two ways seem to stand out amongst traders, short term pair trading, and longer term pair trading.
Short term pair trading is where you may or may not do both sides of the pair at the same time, but are "leaning" on the other leg and trading the other. This is a favorite of traders that like to go flat at the end of the day.
The other way to trade pairs is to put them on both at relatively the same time, and then manage the position by adding or removing some on both sides or one side of the pair, but leaving it in days and sometimes months.
These two ways require vastly different skills and IMHO, different types of anlysis. In the old days, all people used to do was to pick two equitites in the same sector and eyeball the pair for comovement. They then dove in and tried trading it. This worked because there were few that were doing this kind of trading and mistakes were not usually punished.
As more and more people got into it and the pairs became more and more efficient in relation to each other, the analysis started to get more and more sophisitcated, with things like correlation analysis and fundamental analysis being done on the pairs. This too worked for a while. However, recently the money that is left in the markets these days is largely Hedge Funds, and this is a staple strategy for them.
So on the short term, you have high frequency data analysis that is being done because of the highly non-linear relations. And on the longer term, you now have cointegration analisys being done.
This could get technical, but it comes down to the "fact" pairs analsisys is:
"1) Co-dependencies between asset returns may be highly non-linear in nature, but correlation is only a liner measure.
2) Unconditional correlation is essentially a static measure, but dynamic relationships between markets may exist with a non-stable lead-lag nature.
3) Unconditional correlation only exists when the returns are jointly covariance stationary. In other words, correlation estimates jump around because they are being measured on non-jointly stationary series.
To summarize the above, correlation is not a stable measure. The observed instability (in todays pairs) is not (necessarily) due to the lack of joint stationarity, but is a result of non-linear relationships.
At the longer time frames, cointegration analysis allows for the
dynamic co-dependencies in financial markets. In the shorter time frames, you probably need chaotic (attractor) type analysis to deal with the same non-linearity..."
I am developing a software that uses some of these concepts and I hope will allow me to get an edge not only on pairs, but on sector trading (which is a kind of flip side to pair analysis) as well. We'll see if I can couple the software that hones in on good pairs together with my skill in trading...
nitro
Quote from heilbronner:
First, thanks for the answer, nitro.
Maybe you can explain the "mathematics" of _SHORT_TERM pair trading a little more detailed. I'm not sure if I'm with you.