AT Start Date Stats.... question for Map Man or LaurieP or others....

[colorado_rob]

So, I'm doing a little study for my own purposes, that I'll share if the results make any sense and seem to be useful....

As input for this little study, I'm using the start date bar chart for 2017 published on the ATC site:

http://www.appalachiantrail.org/imag...n.jpg?sfvrsn=0

And elsewhere on the ATC site they quote that an estimated 3839 hikers started NOBO in 2017. Yikes! I believe that estimate, because I'm re-hiking the AT with my wife and it sure was a zoo in March last year.

Anyway, if one adds up the total starters in the ATC bar chart, which covers Feb 1 to June 1, the number is about 1352 (I digitized the start numbers by date and summed in Excel). Obviously, the 1352 number and bar chart is based on folks who actually registered, and it is not at all surprising that well less than half are represented.

So the estimated start number is 3839, divided by the registered number of 1352, yields a factor of roughly 2.8. I assume some of the 3839 estimated are outside of the Feb 1-June 1 bar-chart window, but probably not too many, percentage wise, start a thru before Feb 1 or after June 1.

So, my basic question: If I wanted to create a bar chart that reasonably reflects stats on the total number of 3839 starters, should I simply factor the bar chart up by this 2.8 factor? I'd probably use a slightly lower factor to account for very early or very late starters....

This bar chart is key to my little study, and I do realize my results are going to be rough estimates, but I don't want to start with something totally hokey...

There are some extreme data points.... for example, on March 1st, there were 36 registered starters. Factoring by, say, 2.7, means I estimate that 97 people started NOBO last March 1st.

Is this all reasonable?

Thanks in advance for any insights.

[Slo-go'en]

You might not be too far off. Feb 1 to June 1 is 120 days. 3839/120 = 31.9917 people a day. Call it 32. Now we know a lot fewer hikers start in Feb and May, so that ups the average for March and April. Lets guess that 75% start in March or April. Now we have 2880 hikers over 61 days, or 93 hikers per day on average. Since that's an average, some days could have well over 100 starting the same day. That's insane. How can that happen?

I was on Springer on April 28 this year and while it was still pretty busy, no where near 90 people on a single day. Something doesn't seem right with these numbers. I'm probably underestimating the number who start in Feb which are probably concentrated in the last 2 weeks of the month.

[Lauriep]

Did you notice the Amicalola Falls graph here: http://appalachiantrail.org/images/default-source/facilities/amicalola-fsp.jpg?sfvrsn=0. By the way, the old charts are going away soon.

Also, the thru-hiker rosters from Amicalola Falls are factored in to the equation in determining the number of starters.

[map man]

The number registered to start at Springer in 2017 was 1403, and so your 1352 number means that likely 51 hikers registered to start before Feb. 1 or after June 1. The number registered to start at Amicalola Falls State Park instead (a separate graph) was 1709, so add those two together and the number of hikers doing a traditional NOBO in 2017 who registered was 3112 (1403 + 1709). So if ATC is saying that their estimate for traditional NOBOs in 2017 is 3839 then they must believe that around 19% of folks attempting a NOBO thru-hike in 2017 did not register their intention with ATC (so multiply the daily numbers -- derived by adding the daily numbers from both NOBO graphs -- by a factor of 1.23 to get a ballpark estimate of how many started a NOBO thru-hike each day). I don't know how they arrive at that percentage, but they undoubtedly have good reasons. They've been at this a while. One way they could do it is to compare the physical daily head counts that the ridge runner stationed at Amicalola does during NOBO thru hike season and compare it to the daily numbers who registered to start at Amicalola.

Here's a link to their full stats page:

http://www.appalachiantrail.org/home...tration-charts

[colorado_rob]

Thanks Laurie and Mapman! I don't know why I didn't seen that Amicalola chart, that mostly fills in the gaps nicely, than I'll apply that much more reasonable factor.

Now I'm trying to find stats on both speed and drop off points for Springer->NOBO folks (including Amicaloa), and I have a couple old mapman threads I'm studying. The ATC page has Harpers and Katahdin finish percentages, which is a good start. Probably fairly linear between these all, with a couple of step functions at Neels, Damascus and who knows, maybe the Whites. Other threads keep claiming a 20-25% dropout rate at Neels, but I don't believe those. I might assume 10%. Good enough for what I'm doing.

Again, thanks!

[map man]

Thanks Laurie and Mapman! I don't know why I didn't seen that Amicalola chart, that mostly fills in the gaps nicely, than I'll apply that much more reasonable factor.

Now I'm trying to find stats on both speed and drop off points for Springer->NOBO folks (including Amicaloa), and I have a couple old mapman threads I'm studying. The ATC page has Harpers and Katahdin finish percentages, which is a good start. Probably fairly linear between these all, with a couple of step functions at Neels, Damascus and who knows, maybe the Whites. Other threads keep claiming a 20-25% dropout rate at Neels, but I don't believe those. I might assume 10%. Good enough for what I'm doing.

Again, thanks!

Rob, for several years earlier this century ATC gave numbers for Springer, Neels, Fontana, Harpers Ferry and Katahdin. I believe they asked the folks at Mountain Crossings to do a head count for them at Neels, and I imagine they might have gotten the Fontana numbers by asking the people at GSMNP to count the number of thru hiker permits dropped in the box where NOBOs entered the park (though that's just a guess on my part). And their counts in those years confirm your hunch that the estimate of really high dropout rates in the early miles of the AT amount to an urban legend (or should we say rural legend? ). My memory is that the dropout rate at Neels was around 10%, at Fontana was around 20% and at Harpers Ferry was around 50%. Although those numbers are no longer published on the web site it's always possible that ATC still has them and might be willing to share them with you.

My gut tells me that the dropout rates have not changed dramatically in the last decade, and so projections based on that older data are probably still pretty valid. I know I have continued to look at recent hiker years at trailjournals.com (more recent than 2010, the last official year in my NOBO hiking rates study) and see days to complete and zero days taken and so forth are staying remarkably steady over time.

[rompel]

Rob, for several years earlier this century ATC gave numbers for Springer, Neels, Fontana, Harpers Ferry and Katahdin. I believe they asked the folks at Mountain Crossings to do a head count for them at Neels, and I imagine they might have gotten the Fontana numbers by asking the people at GSMNP to count the number of thru hiker permits dropped in the box where NOBOs entered the park (though that's just a guess on my part). And their counts in those years confirm your hunch that the estimate of really high dropout rates in the early miles of the AT amount to an urban legend (or should we say rural legend? ). My memory is that the dropout rate at Neels was around 10%, at Fontana was around 20% and at Harpers Ferry was around 50%. Although those numbers are no longer published on the web site it's always possible that ATC still has them and might be willing to share them with you.

I remember those statistics. As I recall, they got a head count from Mountain Crossings, then inflated it by a fixed amount (20% is my recollection) to estimate the count for Springer.

If ATC doesn't want to dig up those stats for you, they probably still exist in the Wayback Machine.