http://www.djindexes.com/mdsidx/index.cfm?event=showAvgFaq#q21
Circuit Breaker Rules
After the Dow Jones Industrial Average plunged 508 points in
the Oct. 19, 1987, crash, government officials had a question: What
could be done to prevent a replay?
The response was two major new rules implemented in 1988. The first
established circuit breakers that would halt trading for an hour if
the Dow Jones Industrial Average plunged 250 points, and for two
hours if it fell 400 points. The second clamped a collar on the
ability of program traders to dart between stocks and stock index
futures when the Dow industrials rose or fell more than 50 points,
an effort to reduce the volatility such arbitrage trading was said
to cause.
so far no circuit breaks?
trading as per norm?
