RT Journal Article SR Electronic T1 Quantifying Long-Term Market Impact JF The Journal of Portfolio Management FD Institutional Investor Journals SP jpm.2021.1.324 DO 10.3905/jpm.2021.1.324 A1 Harvey, Campbell R. A1 Ledford, Anthony A1 Sciulli, Emidio A1 Ustinov, Philipp A1 Zohren, Stefan YR 2021 UL http://jpm.pm-research.com/content/early/2021/12/28/jpm.2021.1.324.abstract AB Impact costs occur when large buy or sell orders move market prices. The measurement of these costs is crucial for the evaluation of potential trading strategies and the successful execution of systematic investment strategies. However, common approaches suffer from a type of myopia: impact is only measured for the current transaction. In many cases, orders are correlated, and the impact of the first order will affect the execution of future orders. The authors propose a new measure that quantifies the long-term effects of market impact: expected future flow shortfall (EFFS). Their method is both intuitive and straightforward to implement. Importantly, the EFFS method performs competitively with far more complex and data-hungry approaches. The method should be useful for both the evaluation of execution methods and the sizing of orders.