This paper proposes a new method for determining the upper bound of any investment strategy's maximum profit, applied in a given time window [0, T]. This upper bound is defined once all the prices are known at time T and therefore represents the ex-post maximum efficiency of any investment...

The promotion of both market fairness and efficiency has long been a goal of securities market regulators worldwide. Accelerated digital disruption and abusive trading behaviors, such as the GameStop mania, prompt regulatory changes. It is unclear how this "democratization" of trading power...