In airports one often finds oneself standing in a central line that splits into many smaller lines. For example, a single long line for security screening splits near its end into many small lines in front of each screening machine.
The line sorter can create an incentive for people to take less time at the screener if all the fast looking people get to go together. You may have noticed the elite traveler lines sometimes that people can self select into. In a recent trip to Costa Rica, there was a persons travelling without children line that went incredibly faster than the persons with children line. Some line sorters may be serving this function.
Robin, your observation that by being sorted your delay is longer on average than the line you would have chosen is bogus.
Consider these two possibilities
1) Lines are sorted by a mechanism we don't know, with the constraint that all scanning stations are offered traffic constantly.
2) Lines are self-sorted, with the constraint that all scanning stations are offered traffic constantly.
If traffic is offered constantly, the total throughput in 1) and 2) is identical. Then for you to have an average shorter wait time in situation 2) requires that everybody else in the line with you has a slightly longer wait time.
You could only get through the self-chosen line faster by beating out your fellow line-mates.
As to the rest of it, I think the likely ideas have all been hit in these comments. Mostly, make sure people are prepping up to keep offered traffic at the bottleneck steady. Secondarily, I have seen partially hidden screeners that needed traffic directed to them to keep their offered traffic steady. Finally, I have seen these sorters participate in shutting down offered traffic to a station that was closing, and in reconfiguring the line physically to adjust for opening and closing of stations. There real value could be primarily episodic, unrevealed by a cursory glance.
I want to vote these comments up but there is no voting here :-/
It astonishes me that trained economists don't notice something fundamental like this, and instead there is a pile-on to lob gripes about not having been allowed to seize the best outcome - and damn the costs of rent seeking!
Only one or two comments that I can see are paying attention to the nominal point of the entire enterprise - to filter the public as efficiently as possible so that most people are safe from a tiny, criminally insane, handful of people who might try to kill random strangers in the absence of security procedures.
Hasn't anyone noticed the differences from line to line? Some lines have that new radar thing, some lines are closer to chemical sniffers, and so on. Plus I mean, coordination is hard and I bet its good to just rotate people into an easier task every so often so they don't get too bored looking for a gun on a video monitor. If you can have your papers all set, smile, and say thank you for their help then maybe they'd hate their job less.
It seems to me that managing the safety process is the primary thing that matters here... not ridiculous quibbles over autonomy and saving that extra 30 seconds. Especially when I remember the likely inferential distance between myself and the many people who can be safely assumed to be optimizing the process.
If someone can see a significant improvement to make to airport security processes which would produce an obvious aggregate benefit, that would be amazing, but no one seems to be offering that kind of suggestion.
Wasn't the point of this blog to "overcome bias"? And yet so much of the content here seems incredibly biased to me... and I don't think I am substantially crazier than I was two years ago when I thought Robin's content here was pretty good.
Maybe there's something obvious that I'm not noticing? But more than that hypothesis, I find myself wondering whether the process that generates content here is well enough designed that's its worth paying attention to the blog anymore. Did Robin jump the shark at some point? Would Robin notice if he had? Does he have a line of retreat that would make it safe for him to stop posting if that were the right thing to do?
Off-topic, but your fire-the-CEO markets and other posts have rested on the notion that there is a shortcoming in corporate governance that results in CEOs being overpaid. I wasn't aware of anyone who seriously disputed that, but Megan McArdle recently indicated she had changed her mind on it, citing Ed Carr's comparison of public vs privately owned companies. Any thoughts?
Line sorters at airports perform a function of debated utility: They make it more difficult for a security screener and a security evader to cooperate. Of course there's nothing preventing the security screener, security evader, and line sorter form all cooperating together, I suppose.
Thinking about it, I'm not sure line sorters *can* do anything other than change the variance in line-waiting-time.
Thinking about it, it seems to me that moving people around doesn't affect the bottle-neck: the head of the line. If we have 3 scanning stations, and each one is running flatout, then rearranging people before they get to the 3 stations is just rearranging deck chairs on the Titanic. Unless 1 of the stations at some point runs out of people to process, and idles, then they run equally fast no mater how many people are sorted and re-sorted. (It will take you the same amount of time to cut your grass if you go front-back or back-front, so long as you don't stop or repeat sections.)
Security Theater sounds plausible. The appearance of a well-thought out and greased machine is important, and the appearance can be more important than reality.
Covering up individual worker productivity variations seems weak. Passengers care generally about getting through quickly, particularly in comparison to those around them. They don't care if they do this via a slow person but short line, or fast person and longer line.
Don't forget that by random variation alone more people are guaranteed to show up in the longer line for the same reason that more people find themselves on crowded airplanes even when most airplanes are not crowded.
I don't remember seeing line sorters before 9/11. Maybe it's a failure of my memory but quite possibly the line sorters are there to serve some supposed security purpose.
An earlier comment pointed out that certain lines may have higher quality equipment which would be totally wasted if terrorists could simply choose the other lines. However, I think the line sorters often serve another purpose.
The TSA frequently insists they have screeners doing behavioral profiling and they don't reveal who they select for additional observation/checks so terrorists can't reverse engineer the system. This means they need someone standing around watching the queue and somehow selecting people for additional scrutiny. A line sorter is the perfect way to do this and the reason some lines are moving slower may well be that line is exposed to additional scrutiny.
And since "making someone else slower" is an unpriced externality, that means without a line sorter we would spend too much mental effort trying to pick the fastest line (relative to the social optimum).
Because the lines move faster when you put your laptop, shoes, etc.. in the bins before actually reaching the front of the line. If people had to select the screener at the last minute people would have to lug all their bins over to the screener and delay the process.
Those are often the slowest lines since the 16 year old girl hasn't been at the store long enough to know the various produce codes and ends up having to look crap up or call for price checks.
The line sorter can create an incentive for people to take less time at the screener if all the fast looking people get to go together. You may have noticed the elite traveler lines sometimes that people can self select into. In a recent trip to Costa Rica, there was a persons travelling without children line that went incredibly faster than the persons with children line. Some line sorters may be serving this function.
Robin, your observation that by being sorted your delay is longer on average than the line you would have chosen is bogus.
Consider these two possibilities
1) Lines are sorted by a mechanism we don't know, with the constraint that all scanning stations are offered traffic constantly.
2) Lines are self-sorted, with the constraint that all scanning stations are offered traffic constantly.
If traffic is offered constantly, the total throughput in 1) and 2) is identical. Then for you to have an average shorter wait time in situation 2) requires that everybody else in the line with you has a slightly longer wait time.
You could only get through the self-chosen line faster by beating out your fellow line-mates.
As to the rest of it, I think the likely ideas have all been hit in these comments. Mostly, make sure people are prepping up to keep offered traffic at the bottleneck steady. Secondarily, I have seen partially hidden screeners that needed traffic directed to them to keep their offered traffic steady. Finally, I have seen these sorters participate in shutting down offered traffic to a station that was closing, and in reconfiguring the line physically to adjust for opening and closing of stations. There real value could be primarily episodic, unrevealed by a cursory glance.
I want to vote these comments up but there is no voting here :-/
It astonishes me that trained economists don't notice something fundamental like this, and instead there is a pile-on to lob gripes about not having been allowed to seize the best outcome - and damn the costs of rent seeking!
Only one or two comments that I can see are paying attention to the nominal point of the entire enterprise - to filter the public as efficiently as possible so that most people are safe from a tiny, criminally insane, handful of people who might try to kill random strangers in the absence of security procedures.
Hasn't anyone noticed the differences from line to line? Some lines have that new radar thing, some lines are closer to chemical sniffers, and so on. Plus I mean, coordination is hard and I bet its good to just rotate people into an easier task every so often so they don't get too bored looking for a gun on a video monitor. If you can have your papers all set, smile, and say thank you for their help then maybe they'd hate their job less.
It seems to me that managing the safety process is the primary thing that matters here... not ridiculous quibbles over autonomy and saving that extra 30 seconds. Especially when I remember the likely inferential distance between myself and the many people who can be safely assumed to be optimizing the process.
If someone can see a significant improvement to make to airport security processes which would produce an obvious aggregate benefit, that would be amazing, but no one seems to be offering that kind of suggestion.
Wasn't the point of this blog to "overcome bias"? And yet so much of the content here seems incredibly biased to me... and I don't think I am substantially crazier than I was two years ago when I thought Robin's content here was pretty good.
Maybe there's something obvious that I'm not noticing? But more than that hypothesis, I find myself wondering whether the process that generates content here is well enough designed that's its worth paying attention to the blog anymore. Did Robin jump the shark at some point? Would Robin notice if he had? Does he have a line of retreat that would make it safe for him to stop posting if that were the right thing to do?
It's security psychology not security theater.
If someone tells you to do something and you do it, you experience a loss of control. It is a mild form of hypnosis.
How would people in these lines effectively anticipate ahead of time which line is moving faster?
Seems more likely these security staff are just conspiring to have extra trivially easy work.
Off-topic, but your fire-the-CEO markets and other posts have rested on the notion that there is a shortcoming in corporate governance that results in CEOs being overpaid. I wasn't aware of anyone who seriously disputed that, but Megan McArdle recently indicated she had changed her mind on it, citing Ed Carr's comparison of public vs privately owned companies. Any thoughts?
Line sorters at airports perform a function of debated utility: They make it more difficult for a security screener and a security evader to cooperate. Of course there's nothing preventing the security screener, security evader, and line sorter form all cooperating together, I suppose.
Thinking about it, I'm not sure line sorters *can* do anything other than change the variance in line-waiting-time.
Thinking about it, it seems to me that moving people around doesn't affect the bottle-neck: the head of the line. If we have 3 scanning stations, and each one is running flatout, then rearranging people before they get to the 3 stations is just rearranging deck chairs on the Titanic. Unless 1 of the stations at some point runs out of people to process, and idles, then they run equally fast no mater how many people are sorted and re-sorted. (It will take you the same amount of time to cut your grass if you go front-back or back-front, so long as you don't stop or repeat sections.)
A variation on security theatre is security ritual.
Security Theater sounds plausible. The appearance of a well-thought out and greased machine is important, and the appearance can be more important than reality.
Covering up individual worker productivity variations seems weak. Passengers care generally about getting through quickly, particularly in comparison to those around them. They don't care if they do this via a slow person but short line, or fast person and longer line.
More people will wind up in the line with the highest *throughput*, much like planes.
Don't forget that by random variation alone more people are guaranteed to show up in the longer line for the same reason that more people find themselves on crowded airplanes even when most airplanes are not crowded.
I don't remember seeing line sorters before 9/11. Maybe it's a failure of my memory but quite possibly the line sorters are there to serve some supposed security purpose.
An earlier comment pointed out that certain lines may have higher quality equipment which would be totally wasted if terrorists could simply choose the other lines. However, I think the line sorters often serve another purpose.
The TSA frequently insists they have screeners doing behavioral profiling and they don't reveal who they select for additional observation/checks so terrorists can't reverse engineer the system. This means they need someone standing around watching the queue and somehow selecting people for additional scrutiny. A line sorter is the perfect way to do this and the reason some lines are moving slower may well be that line is exposed to additional scrutiny.
And since "making someone else slower" is an unpriced externality, that means without a line sorter we would spend too much mental effort trying to pick the fastest line (relative to the social optimum).
Because the lines move faster when you put your laptop, shoes, etc.. in the bins before actually reaching the front of the line. If people had to select the screener at the last minute people would have to lug all their bins over to the screener and delay the process.
Because they are prettier to look at?
Those are often the slowest lines since the 16 year old girl hasn't been at the store long enough to know the various produce codes and ends up having to look crap up or call for price checks.