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Imperfect Market Monitoring and SOES Trading


  • FOUCAULT, Thierry
  • RÖELL, Ailsa

    (Princeton University)

  • SANDAS, Patrik

    (The Wharton School)


We develop a model of price formation in a dealership market where monitoring of the information flow requires costly effort. The result is imperfect monitoring, which creates profit opportunities for speculators, who do not act as dealers but simply monitor the information flow and quote updates in order to pick off stale quotes. Externalities associated with monitoring can help to sustain non-competitive spreads. We show that protecting dealers against the execution of stale quotes can result in larger spreads and be detrimental to price discovery due to externalities in monitoring. A reduction in the minimum quoted depth will reduce the spread and speculators' trading frequency. Our analysis is relevant for the SOES debate given that the behavior of speculators in our model is very similar to the alleged behavior of the real world SOES bandits.

Suggested Citation

  • FOUCAULT, Thierry & RÖELL, Ailsa & SANDAS, Patrik, 1999. "Imperfect Market Monitoring and SOES Trading," Les Cahiers de Recherche 671, HEC Paris.
  • Handle: RePEc:ebg:heccah:0671

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    References listed on IDEAS

    1. Harris, Jeffrey H. & Schultz, Paul H., 1998. "The trading profits of SOES bandits," Journal of Financial Economics, Elsevier, vol. 50(1), pages 39-62, October.
    2. Kandel, Eugene & Marx, Leslie M., 1997. "Nasdaq market structure and spread patterns," Journal of Financial Economics, Elsevier, vol. 45(1), pages 61-89, July.
    3. Drew Fudenberg & Jean Tirole, 1991. "Game Theory," MIT Press Books, The MIT Press, edition 1, volume 1, number 0262061414, January.
    4. Kandel, Eugene & M. Marx, Leslie, 1999. "Odd-eighth avoidance as a defense against SOES bandits," Journal of Financial Economics, Elsevier, vol. 51(1), pages 85-102, January.
    5. Michael J. Barclay & William G. Christie & Jeffrey H. Harris & Eugene Kandel & Paul H. Schultz, 1999. "Effects of Market Reform on the Trading Costs and Depths of Nasdaq Stocks," Journal of Finance, American Finance Association, vol. 54(1), pages 1-34, February.
    6. Battalio, Robert H. & Hatch, Brian & Jennings, Robert, 1997. "SOES Trading and Market Volatility," Journal of Financial and Quantitative Analysis, Cambridge University Press, vol. 32(02), pages 225-238, June.
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    Cited by:

    1. Liu, Wai-Man & Sawyer, K. R., 2003. "How free are free trading options?," Pacific-Basin Finance Journal, Elsevier, vol. 11(5), pages 573-591, November.

    More about this item


    monitoring; bid-ask spread; automatic execution; SOES trading;

    JEL classification:

    • C53 - Mathematical and Quantitative Methods - - Econometric Modeling - - - Forecasting and Prediction Models; Simulation Methods
    • E30 - Macroeconomics and Monetary Economics - - Prices, Business Fluctuations, and Cycles - - - General (includes Measurement and Data)


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