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Circuit Breakers and the Tail Index of Equity Returns


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  • John Galbraith


  • Serguei Zernov


Using the tail index of returns on US equities as a summary measure of extreme behaviour, we examine changes in the equity markets surrounding the development of program trading for portfolio insurance, the crash of 1987, and the subsequent introduction of circuit breakers and other changes in market architecture. Recently-developed tests for the null of constancy of the tail index, versus the alternative of a change at an unknown date, permit inference on changes in extreme behaviour over a long time period while allowing for second-moment dependence in the return data. We find strong evidence of a decrease in the tail index (increase in the probability of extreme events) around the beginning of large scale program trading, and weaker, but still substantial, evidence of further significant change in the tail index following the introduction of circuit breakers. Point estimates of the tail index suggest that the tail index has nonetheless not regained pre-program-trading levels. Utilisant l'indice de queue de distribution (index tail) des rendements financiers sur actions dans les marchés américains comme mesure sommaire des comportements extrêmes, nous examinons les changements dans le marché des actions entourant le développement de programmes automatiques de transaction (Trading Program) pour l'assurance de portefeuille, le krach de 1987, l'introduction des coupe-circuits et autres changements dans les systèmes financiers. De nouveaux tests, récemment développés, permettent l'inférence statistique sur le changement des comportements extrêmes sur une longue période ; tests qui sont valides dans le cas d'hétéroscédasticité conditionnelle. L'hypothèse nulle est que l'indice de queue de distribution est constant alors que l'hypothèse alternative est le changement de cet indice à une date inconnue. Nous avons trouvé de manière très significative que d'une part, l'indice de queue de distribution a diminué (la probabilité d'évènements extrêmes a augmenté) au début de la période des programmes de transactions. D'autre part, l'introduction de coupe-circuits a augmenté cet indice mais est resté plus faible que sa valeur avant l'introduction des programmes de transactions. Les estimateurs de l'indice de queue de distribution suggèrent qu'il n'a pas retrouvé sa valeur initiale.

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Bibliographic Info

Paper provided by CIRANO in its series CIRANO Working Papers with number 2002s-62.

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Date of creation: 01 Jun 2002
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Handle: RePEc:cir:cirwor:2002s-62

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Keywords: Circuit breaker; structural change tests; tail index; Coupe-circuits; tests sur le changement structurel; indice de queue de distribution;

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  1. Phillip Kearns & Adrian Pagan, 1997. "Estimating The Density Tail Index For Financial Time Series," The Review of Economics and Statistics, MIT Press, vol. 79(2), pages 171-175, May.
  2. Loretan, Mico & Phillips, Peter C. B., 1994. "Testing the covariance stationarity of heavy-tailed time series: An overview of the theory with applications to several financial datasets," Journal of Empirical Finance, Elsevier, vol. 1(2), pages 211-248, January.
  3. G. Booth & John Broussard, 1998. "Setting NYSE Circuit Breaker Triggers," Journal of Financial Services Research, Springer, vol. 13(3), pages 187-204, June.
  4. Quintos, Carmela & Fan, Zhenhong & Phillips, Peter C B, 2001. "Structural Change Tests in Tail Behaviour and the Asian Crisis," Review of Economic Studies, Wiley Blackwell, vol. 68(3), pages 633-63, July.
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Cited by:
  1. Wagner, Niklas, 2005. "Autoregressive conditional tail behavior and results on Government bond yield spreads," International Review of Financial Analysis, Elsevier, vol. 14(2), pages 247-261.
  2. Bryan Kelly & Hao Jiang, 2013. "Tail Risk and Asset Prices," NBER Working Papers 19375, National Bureau of Economic Research, Inc.
  3. Straetmans, Stefan & Candelon, Bertrand, 2013. "Long-term asset tail risks in developed and emerging markets," Journal of Banking & Finance, Elsevier, vol. 37(6), pages 1832-1844.
  4. John G. Galbraith & Serguei Zernov, 2006. "Extreme Dependence In The Nasdaq And S&P Composite Indexes," Departmental Working Papers 2006-14, McGill University, Department of Economics.


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