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This is official policy, but not "common practice." According to CNBC: "These circuit breakers have never been triggered in their current form during regular t

• uptown 7y ago
  The current circuit breaker rules went into effect in early 2013. There were different rules in-place prior to that date.
  • sdinsn 7y ago
    And under all rules, the last time it happened was 1997, so it's still signficant