Statistical arbitrage : Can a pairs trading strategy beat a buy-and-hold strategy?

Abstract: In this thesis, the aim is to investigate whether a pairs trading strategy on Swedish stocks can generate a higher risk-adjusted return compared to a buy-and-hold strategy on a benchmark index. The benchmark index is the OMX Stockholm Benchmark-index (OMXSBPI), which is an index that should reflect the Swedish market in general. With a statistical focus, a trading algorithm is built which is then evaluated on data between the years 2018 to 2021. The statistical concepts this thesis is based on are stationarity and cointegration and it is the Augmented Dickey-Fuller test that forms the basis for being able to test these concepts. The risk-adjusted return for the strategy is evaluated using the popular measure Sharpe ratio, which is then compared to the Sharpe ratio for the OMXSBPI-index. The results obtained in this study can not confirm that the pairs trading strategy is better than a buy-and-hold strategy on the OMXSBPI-index in terms of risk-adjusted return. One indication, however, is that the strategy seems to perform better in conditions when the market is declining. In 2018, the index went down by 7.7060 while the strategy went up by 7.5100 percent. As it is data for only one year, it is not possible to determine whether it is due to chance or a potential edge of the strategy.