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The Math of the Tie

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.


5 Responses

  1. Marty. You spoke about the tie and the metal particles and how they could lead to the type of job DB Cooper may have had. However, I spoke with Tom Kaye and Geoffrey Grey. The titanium particle were common in white paint which was on the tie clip. So, its possible the metal particle have nothing to do with Cooper’s profession. Its possible that they were just from the white paint flecks that were found on the tie. Funny how you left that out. James Date: Fri, 22 Apr 2016 04:50:24 +0000 To: curl88 (at) hotmail.com

    • Kaye’s findings are available for all to see online:


      “Working upstream in the production process, the titanium sponge plants used sodium, chlorine and magnesium of which sodium and chlorine were prevalent on the tie. This sparked an extensive investigation into the companies involved and the production processes. Original samples of titanium sponge from the 1970’s were obtained [2] for comparison. Titanium sponge particles have a distinctive appearance and the second sampling of the tie should have been thorough enough to produce sponge samples, but no identifiable sponge particles were found.”

      It’s not just the titanium either, there are other metallic particles which indicate the machining of anti-corrosive metal parts.

  2. Jo Weber had many conversation with Gunther and several letters,
    He went thur his book with me page by page and told me to have a highlighter and tabs…I did as he said…his story was developed thru 6 conversation with a woman who claimed to know Cooper and to know Gunther…I know how they knew each other – but unless you want to read his letter to me and view the book he had me mark up and talk to the woman who contacted him…(she is deceased), but contacted me before she died and when I called back was told she passed away 2 hours prior). Since her call came to me in the middile of the night after I remarried I could not let her have my new phone number…but I would call her very 3 months to check on her…her last conversation with me was BEGGING me for an address so she could mail something to me…but my husband did NOT want her to have our address or phone number as she was know to call during the wee hours of the night and early morning and usually intoxicated until she was put in a facility.

    I spoke with her daughter after she died and asked it there was anything in her mothers belonging her mother wanted me to have..she had no idea what it might have been.

  3. […] “The Math of the Tie” by Marty Andrade. martyandrade.wordpress.com. 22 April 2016. […]

  4. […] Common sense suggests the tie belonged to Cooper, trying to connect it to him the way I did in my Math Tie post may have been a futile endeavor. Definitely give the podcast a […]

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