This paper derives a robust online equity trading algorithm that achieves the greatest possible percentage of the final wealth of the best pairs rebalancing rule in hindsight. A pairs rebalancing rule chooses some pair of stocks in the market and then perpetually executes rebalancing trades so...

For a market with m assets and T discrete trading sessions, Cover and Ordentlich (1998) found that the “Cost of Achieving the Best Rebalancing Rule in Hindsight” is p(T, m) = _{n₁ ···^Σ n_m=T} (n₁,^T...,n_m)(n₁/T)(n₁ · · · (n_m/T)^n_m. Their super-replicating strategy is impossible to compute...