Many in the Cooper world believe the tie Cooper left behind on the airplane could have been purchased at a thrift store. Indeed, because of the unique mixture of metallic particles on the tie, this is necessary to save their preferred suspect from being eliminated from the case. And truthfully, a tie picked at random from a thrift store had to belong to somebody. The odds of picking a tie belonging to a specific person are very low, but since every tie belongs to somebody with their own background and habits, it’s possible Cooper’s tie has nothing to do with Cooper himself.
But how unlikely is it?
First, Tom Kaye was able to connect the tie to Cooper. The tie belonged to someone who smoked a lot while wearing the tie over a long period of time. We know Cooper smoked and that 44% of men smoked in 1971. Cooper used matches from matchbooks to light his cigarettes. Once again, Kaye found particle evidence on the tie indicating matchbooks were the preferred ignition source for whomever owned the tie for those many years of wear before the hijacking. There is no data on ignition source preferences among smokers in 1971. I would guess it would be about half the population, the other half would use lighters or stick matches.
Therefore, even though we can’t get an exact figure, we can roughly estimate the probability of someone randomly picking a tie at a thrift store which matches their own smoking habits and preferred ignition source at 22%. Or, put another way, there is a 78% chance the tie belonged to Cooper long before the hijacking ever happened. If some evidence was found that Cooper was left handed (other than the placement of the tie tack itself), we could be over 97% certain the tie belonged to Cooper.
There’s another wrinkle here. Not only does the tie have to match Cooper’s habits by chance, Max Gunther has to match Dan LeClair’s career and life to what was later found on the tie, again by random chance. There are two ways of looking at this question, one is through the real distribution of jobs, the second is by using the number of jobs Gunther could have picked from if he picked one at random from a list.
Using the actual distribution of the labor force, Gunther would have to pick a white collar job in the manufacturing sector. According to the 1970 Census, manufacturing accounted for 27% of the workforce. White collar work accounted for about 47% of jobs. Taken together, there is a 13% chance Gunther would pick the right job in the right sector. We’ll use this as our low estimate.
It is unlikely, in my mind, that Gunther would be even thinking about the distribution of jobs if he were creating a fictional story.* Rather, he would likely choose from jobs he, as a journalist and author, would be familiar with. And likely, he would be familiar with many many jobs and careers. In the 1970 Census, they profile more than 400 different jobs and careers by category and sector. If Gunther just picked something at random, we can safely say he had about 400 real choices.
So, on the conservative side of our estimate, there is a 13% chance Gunther picks the right sector and type of work, and there’s a 44% chance Dan Cooper picks a tie at random that matches his smoking habit (ignoring, for a moment, the matchbook question); doing some basic probability calculations, there’s only a 5.7% chance of these two events aligning in the way they have in this case. More realistically, we can say that there were over 400 possible careers for Gunther to choose from, and using the 22% estimate about Cooper picking a tie at random from earlier, we got the chance of these two independent events aligning at about 1.1 in 2000.
Yes, there’s room to disagree about some of the particulars. You can adjust the parameters as you see fit. Regardless, this is a highly unlikely circumstance. We are asked to believe that Dan Cooper, living in the Pacific Northwest in 1971, bought a tie at a thrift store to wear on his hijacking and that tie would later prove to have particles that could have only been obtained in an esoteric industrial situation. Then we would have to believe an author living in Connecticut over a decade later would pick that same situation for his fictional DB Cooper character for a fake story he hoped would dupe enough people to make him some money. What side of the bet would you like to be on?
*This is a major reason why I don’t think Gunther is making any of this up. A novelist chooses the careers of his character for some specific purpose. He needs a rich character, or a miserable character, or some other quality to help move the plot. Picking industrial chemicals doesn’t add anything to the character of Dan LeClair.