Issues in Assessing Trade Execution Costs

Abstract

This study assesses the sensitivity of trading cost estimates to two methodological issues: the time adjustment made before comparing trades to quotes, and the procedure used to designate trades as buyer or seller-initiated. Consistent with recent research for Nasdaq stocks, the results indicate that making no allowance for trade reporting lags is optimal when assessing whether trades are buyer or seller initiated, for both Nasdaq and NYSE stocks. However, the evidence also indicates that trade prices are best compared to earlier quotations when assessing trade execution costs, in order to capture the effect of quotations systematically rising (falling) in the seconds before customer buy (sell) orders are completed. The results also indicate that a technique for inferring trade direction recommended by Ellis, Michaely, and O'Hara (2000) leads to significantly smaller estimates of trading costs than the well-known Lee and Ready (1994) algorithm. Finally, despite the sensitivity of trading cost measures to these methodological issues, inference as to whether the Nasdaq dealer market or the NYSE auction market provides lower trade execution costs is not sensitive.

Keywords: Trade execution costs, dealer versus auction markets, trade reporting lags

JEL Classification: G12