Sharpening Shapley Allocation: from Basel 2.5 to FRTB
The paper argues that Shapley allocation is the most suitable risk allocation method for financial institutions, balancing theoretical properties, accuracy, and practicality. It overcomes perceived computational intractability by replacing the exponential analytical approach with an efficient Monte Carlo algorithm that scales linearly and becomes preferable for ≥10-14 units. The study proposes solutions for negative allocations, a consistent multi-level hierarchical framework (PTD, CTD, BU approaches), and demonstrates applicability to large trading portfolios under Basel 2.5 and FRTB regimes, showing Shapley better captures diversification and hedging effects compared to simpler methods.