Index arbitrage is a well-established trading strategy. In particular, arbitrage between a stock index futures contract and the underlying basket of stocks is a classical approach.
Reference [1] revisits this technique and proposes a new method called the Basis Mean-Reverting Basket (BMRB) for index arbitrage. Essentially, the authors develop an optimization algorithm to maximize the speed of mean reversion of the basis in price space while incorporating constraints specific to index arbitrage, such as long-only spot positions. The algorithm selects stocks and their weights to maximize the speed of mean reversion while keeping tracking error within acceptable limits.
The authors use Japanese TOPIX futures and constituent stocks from January 2016 to January 2026. They employ rolling 504-trading-day windows with monthly portfolio rebalancing. Trading positions are entered when the basis z-score exceeds a specified threshold and exited when the basis approaches its estimated mean, with a stop-loss threshold also applied.
They pointed out,
This paper proposed the Basis Mean-Reverting Basket (BMRB), a new basket construction method for arbitrage between a stock index futures contract and a spot basket. The problem is formulated to directly optimize the mean reversion of the basis series in price space while constraining the tracking error. An empirical analysis on the Japanese TOPIX market demonstrated the effectiveness of BMRB along three dimensions, in-sample stationarity, out-of-sample arbitrage performance, and robustness to hyperparameters.
In short, the results show that BMRB produces a substantially more mean-reverting price difference than conventional index-tracking and portfolio construction methods. In out-of-sample testing from 2021 to 2026, BMRB achieves an annualized return of 3.80%, a Sharpe ratio of 1.00, and a maximum drawdown of 4.78%, outperforming the competing methods in annualized return. The results are also relatively robust to changes in portfolio size and rebalancing frequency.
The study has limitations, notably that transaction costs and slippage are not considered. Nevertheless, it provides a useful illustration of how optimization can be applied in quantitative trading and highlights the importance of walk-forward analysis.
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References
[1] Hirohashi, K., Kubo, K., & Nakagawa, K. (2026), Basis mean-reverting basket: A unified formulation of index tracking and mean-reverting portfolio for index arbitrage, 2026 IEEE Symposium on Computational Intelligence for Financial Engineering and Economics (CIFEr), 300–307.
Originally Published Here: Optimizing Index Arbitrage Through Mean Reversion
source https://harbourfronts.com/optimizing-index-arbitrage-mean-reversion/