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US vs Non-US Last Logs

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In my post of 17-Oct-21, I presented a survivorship curve based on the number of drops achieved by my entire collection of trackables, active and missing. Using the same data set, I sorted the trackables based on their last log locations (last-logs) in the United States (US) versus locations outside the US, which are mostly in Canada and Europe.   


In the first graph below, the blue line is exactly the same survivorship curve, but with two minor format changes.  In the previous graph, the vertical scale was expressed as a percentage of the total, whereas this scale is total trackables.  Secondly, the horizonal scale is compressed because of the manner I tabulated the data.  The zero drop is the number of trackable released, but all the other drops represent pooled data to maintain my sorting spreadsheet at a manageable size. The value for five drops is actually the pool for drops five through nine, and for ten drops, it is ten through fourteen, and so on.  The rationale will be clear in a later post, when I display the tables.


To obtain the last-logs required visiting the home page of more than a thousand trackables having five or more drops. I started this particular effort on 22 Sep and finished on 20 Oct.  Thus, although I would have wanted otherwise, it is likely some trackables are no longer at the locations initially recorded, and some trackables moved before the survey was complete. The last-logs were tabulated for each US state, and for each country…island protectorates were treated as distinct, to illustrate the geographic reach of trackables (details not shown here). For reasons that escape me now, I did not separate my trackables in Canada to her large provinces and territories. 


In the first graph, the orange line represents trackables having their last logs in the US. Clearly, it is the chief influence on the shape of the survivorship curve for all trackables (the blue line).  It is characterized by the precipitous losses in the first third of the curve, made more dramatic by the data pooling mentioned above. The difference between the lines is the comparatively small number of trackables with last logs outside the US (the gray line). 


Removing the zero and five drops from the graph reduces the scale and permits a detailed look at the bottom of the curve…it reveals some interesting circumstances (see the second graph and appended table below). The first is there is a point between 15 and 20 drops (3.5 to 4.0 years, on average) where the orange and gray lines cross, which means that most of my trackables of that age are not in the US.  It also means that the shape of the survivorship curve after 15-20 drops is dictated by trackable outside the US...the attenuation noted in an earlier post.


Next, the contiguous gray line extends to 78 drops (more than nine years, on average), while the contiguous orange line stops at about 40 drops (six years, on average). There are two US, last-logs at 55 drops that do not show in the graph.  While both trackables were released in the US (TB2T1NF, TB48HKK) , their longevity was augmented by time spent in Europe, where trackables receive much wider respect.  Obviously, it is rare for a trackable that has never left the US to survive as many as 30 drops, especially given that half will disappear before five drops. A curiosity of the gray line is the step-wise shape, somewhat like waves on a beach.  Perhaps it is a manifestation of a seasonal influx of trackables to Europe, something that has fallen off with Covid travel restrictions.


A word of caution going forward. The reader should not interpret the gray line as a survivorship curve for trackables outside the US. I will show in a later post that there are more than twice as many of my trackables outside the US as have been released there.  This means trackables leaving the US, to some as yet unmeasured extent, overwhelm and conceal the actual, non-US attrition.  To get at the true rate-of-loss for both populations, one must identify and test inactive (missing) trackables that never left the US against those trackables that have never been to the US.  That is a future project that must wait until I have an adequate sample of inactive, non-US trackables.



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This is brilliant, I love your reports. It's good to see hard data with a large sample set.


I wonder how much the data would be affected by re-release of proxies after specific criteria are met (such as TB not getting a log after a year)? Depending on how the data was tabulated, I'd imagine it'd either be more of the same, just more data sets or a saw-tooth pattern, with each re-release causing a spike followed by another loss curve.


It'd be interesting to have hard numbers on attrition rate for real TB losses (shiny and new being kept) vs proxies (people deliberately discarding them for not being real)?

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I did a handful of those some years ago (using the copy tags), and annoyingly, two of the originals showed up again, confounding my record-keeping...never again!


If I am ever tempted to do it again I will just look at the attached table.  It was originally put out several years ago, but this one is current. It shows that the vast majority (93+ %) of my trackables are dropped within a year of retrieval, but there are enough of those "others" that I don't want to risk it.   This table is one of the ways I use the elapsed time between drops on my spreadsheets.  I recently had one of my bugs show up after a 10-year absence.  


This table is also the basis for my using three years of inactivity to consider a trackable missing.  Anything inactive for more than three years has a much less than 1% chance of reappearing.  If it does, I just deal with it.



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12 hours ago, shellbadger said:

I recently had one of my bugs show up after a 10-year absence.


I had to go and look it up to double check, but I'd recently seen Kayfabe TB show up after being missing for ten years and a few days. I thought it might have been yours, but that's owned by a deleted account. Good to know that some turn up after a decade - but that's some long odds!


Your data is very educational. I've got a few proxies out (I only send the proxies and keep the originals at home), and I've had my first get "officially" be recognised as lost and moved from the last cache it was in to Unknown Location. Not sure that I'll have the patience to wait the full three years before I send out a replacement, but for me half the fun is in making the replacements anyway.

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