Tuesday, November 4, 2008

Black Swans and Factoids

For the last month, I've been wandering around noticing the absence of new car tags on the road--those paper temporary tags the dealer gives you to drive off the lot and keep your car legal for the 30 days or so it takes to get the permanent plates. Then, over the weekend, in Parking Structure 3 in downtown Portland, Oregon, I spotted paper tags on a brand new Subaru Forester. So much for that particular Black Swan.

Yesterday car sales numbers came out. Today the analysts are parsing the numbers, making sense of a situation that can only honestly be summed up as, 'it's really bad for anybody in that business, but who in their right mind would buy a new car today?"

So, I guess I stop going around telling people I haven't seen any new car tags since I can remember, and start going around quoting the reported numbers and using my annecdotal evidence (a single new car tag) to buttress my point. It's no longer a Black Swan, but it's a factoid. (That in itself may be the problem with Taleb's commercially very successful molehill).

Absence of evidence is not evidence of absence. On the other hand, evidence itself doesn't mean much without taking into account measurement error, calibration assumptions and equipment design tolerances.

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