On 28 January 1986 the space shuttle Challenger broke apart 73 seconds after launch, and all seven of its crew died: Dick Scobee, Michael Smith, Ellison Onizuka, Judith Resnik, Ronald McNair, Christa McAuliffe and Gregory Jarvis.

Four big firms had built the main parts. Thirteen minutes after the accident, so many people were selling one of them, Morton Thiokol, that trading in it was halted, at a price barely changed. When it reopened it sank, and by the close it was down almost 12 percent while the other three were down between 1 and 5. Four months later the presidential commission named the cause: the failure of a seal in a joint of the right booster rocket. Thiokol built the boosters.

Two economists, Michael Maloney and Harold Mulherin, went through the day's trades in 2003. They found no reported insider selling and nobody who made much money, and they say plainly that they could not tell how the price got there. Their best guess is that a price adds up what many people each half-know.

It is still a guess. In 2003, after the shuttle Columbia was lost, the booster maker's stock fell almost 12 percent again, and that time the boosters were not the cause. A smaller firm that depends on the shuttle would fall hardest either way.

Which of the four would you have picked?

Sources: Maloney and Mulherin, "The complexity of price discovery in an efficient market: the stock market reaction to the Challenger crash", Journal of Corporate Finance 9, 2003; Report of the Presidential Commission on the Space Shuttle Challenger Accident, 6 June 1986; Daniel Gross, "The Disaster Market", Slate, 8 August 2003.
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