08 January 2008

Probability and Disaster

On this date in 1906, 1908, 1962, etc, etc ...

By any measure, January the Eighth is an unusually tragic day. There may have been more separate events known popularly as "disasters" on this day than on any other of the year.

In 1906, a landslide in New York state killed 20 people. In 1908, it was a train collision in New York City. In 1962, another train wreck in Holland. Plane crashes in 1989 and 1996. An earthquake in 2006.

Even with all the disasters in world history, both natural and man-made, January 8th seems unusually rife with tragedy, and it is. Considering how rare train wrecks and plane crashes are, to have a combined four on the same calendar day within a century is a bit odd. But is it statistically notable, or just a blip on the radar, a random association of events?

In order to be fair in looking at how unusual the congregation of disasters on January 8th is, we have to define disaster in its various forms. It might be a bit morbid, but bear with me. I will define a major air disaster as one which kills 100 people or more. There have been 76 such crashes worldwide, and two occurred on January 8th. That's more than the average if they were evenly spread (about one disaster every 4 or 5 calendar days). Let's call it about 8x background levels.

There have been 48 train disasters on record, using the same criteria of 100 deaths. Fortunately for those souls aboard both trains that crashed on January 8ths, neither of them were so deadly, and statistics are harder to find on smaller crashes.

I'm losing my point a bit. It is tempting to take a look at the history of such days and look for patterns, and there may be patterns, or at least a lack of complete randomness, but it's pretty weak. Travel is much more intensive during the holiday season, and we're coming to the end of that season, so more transport inevitably means more accidents. Beyond that, though, I wouldn't run to the bomb shelter just yet. January 8th is as safe as any other day.

Tomorrow, The Great Northwest Gale

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