How do I calculate Liquidity-Adjusted VaR using the bid-ask spread method?

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AcadiFi · Accepted Answer

LVaR adds a liquidity cost term to conventional VaR. The spread-based approach: LVaR = VaR + 0.5 * P * (mean_spread + k * spread_stdev), where P is position value, spread is expressed as a percentage (ask-bid)/mid, and k is a confidence multiplier (e.g., 2.33 for 99%). Example: Hollowford Specialty Chemicals position value P=$8,000,000, 99% 1-day VaR from price risk = $186,000, mean proportional bid-ask spread = 0.42%, spread stdev = 0.18%, confidence k=2.33. Liquidity cost = 0.5 * 8,000,000 * (0.0042 + 2.33*0.0018) = 0.5 * 8,000,000 * 0.008394 = $33,576. LVaR = 186,000 + 33,576 = $219,576. The 0.5 factor represents half the round-trip cost — you only pay the spread once when exiting the position. The k*stdev term accounts for stress scenarios where spreads widen beyond normal. ```mermaid flowchart LR A[Standard VaR
price risk] --> C[LVaR] B[0.5 * P *
spread cost] --> C C --> D[Total capital at risk] ``` Limitations: assumes the full position can be liquidated at prevailing spread, ignores market impact (price moves as you sell). For large positions or illiquid assets, combine with the market-impact adjustment. Also assumes spread distribution is stable, which is violated during crises when spreads can widen 5-10x normal levels, so scenario-based stressed spreads are often added.

How do I calculate Liquidity-Adjusted VaR using the bid-ask spread method?

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