Asymmetrical Information

Doesn't randomizing a price around a constant mean (in this case a time price) increase expected consumer surplus?

I'm not sure that's really right, Jane. The unified queue does not reduce average service time, as long as customers are free to slide over to a vacant register. All it does is reduce the variance of wait times.

Me? I like the different queues. I size up both the cashiers, and the likeliness of the people in the queue to pay cash. Because only 5% of people bother with such an exercise, I can usually beat the average wait time.

Either method lets you observe that the gene that governs getting your wallet out ready to pay resides on the Y chromosome.

The universal queue is just symptomatic of the nanny state trying to protect the weak, while those who are resourceful enough to pick the fastest route to checkout are unfairly punished. In fact, this whole business of "first-come first-served" is immoral. Checkout should be auctioned off to the highest bidder. That way, the people who value leaving the store, and who have earned the power to do so wil be rewarded.

And this is America, Goddamnit! We don't "queue up". We wait in line.

I size up both the cashiers, and the likeliness of the people in the queue to pay cash. Because only 5% of people bother with such an exercise, I can usually beat the average wait time.

This is like claiming to be able to beat the market just because you're smart. At my local grocery store, everyone is sizing up the lines, constantly, and sort of rearranging themselves last minute as soon as a checkbook is flashed or a cashier leans toward the microphone. Thus, no one wins. Interestingly, my local store is a Whole Foods, which has not adopted the practice so beloved by the NYT at the Manhattan branch.

At a local (Seattle) state run liquor store I had a cashier tell me to form 2 lines when I managed through my own sheer willpower to form one line behind me. Yes, I am a superman when it comes to buying booze.

Anyway she said that it was faster for her if she had the next person lined up. I told her that it would be true if there wasn't a 30 second wait for the ancient credit card machine to work. She actually grew agitated about this.

Coming from her standpoint I can see why: it makes no difference to her if there is one line or hundreds. She just does her job. From everyone else's (the customers to the owner of the shop) it is better for them to have the UniLine (tm me).

Also in this same shop there's always someone in the back. Doing what I'm not sure -- I usually yell at them to get me a bottle of scotch of the kind that they only store the box in on the shelves.

Again, there's no reason for these workers to see that there's long line and to stop what they are doing. They get paid per hour no matter what.

Oh and thanks to WA state's liquor laws the state is the only one that can run a store. So I'm not looking to this improving any time soon.

If I remember my discrete simulation class, both the single queue and multi queue should have the same average service time per customer and the same throughput, but the single queue will reduce variance, as Bob Dolina mentioned, and inter-customer delays, as well as maximize utilization. What's interesting to me is that some types of places use single queues uniformly (banks, post offices) and others multiple queues (supermarkets, concession stands). Even factoring in all the perceptual psychologies of the customers, shouldn't one model be dominant for almost all situations?

As a side note, I used to frequent the same Rite Aid that Becks mentions, and they have some of the slowest cashiers in the city.

"This is like claiming to be able to beat the market just because you're smart"

Actually, no. This is like saying you can beat the market because you have better information. I know which cashiers are slow if I shop there frequently, while many people don't shop there frequently.

Markets can be "beaten" because they are never perfect. Supermarket checkout lines are significantly less perfect markets than most.

As a general rule, I find it better to get in line behind men at the supermarket. Women are more likely to have coupons, which can slow down the checkout process. Women also are much more likely to pay by check.

What's interesting to me is that some types of places use single queues uniformly (banks, post offices) and others multiple queues (supermarkets, concession stands).

My theory: there's a much greater variation in processing time per customer at a bank or post office than at a supermarket or concession stand. Single queues therefore make more sense at banks and post offices.

there's a much greater variation in processing time per customer at a bank or post office than at a supermarket or concession stand. Single queues therefore make more sense at banks and post offices.

I like the theory. The Social Security office does the same thing, for similar reasons.

I do know of drug stores with single lines, as well as other retail stores, like some Best Buys. Also the Chik-Fil-A at Fairoaks Mall in Fairfax does a single line as well.

The multiple lines in grocery stores do seem to be conducive to having the candy, tabloids, and other impulse buys nicely lined up in a way that might not work as well with a single line.

The reason for multiple lines in grocery stores I think is far more mundane: there's no space for it. When you have twenty cashiers in the front of the store, stretching across 100 feet, separated from the goods by about 8 feet, where are you going to put the massive single queue?

This used to annoy me. But, if a single queue does lead to a delay between customers, then it will make the average time worse. Haven't you ever pointed out to the person in front of you that a clerk/agent is ready for them? Every time that happens, throughput goes down. It's much easier to be attentive to when one specific clerk is ready than to several.

Considering how carefully Duane Reade (the biggest culprit in my experience) optimizes other things, I'm inclined to believe that they're right about this. Considering how competitive and low-margin retail is, shouldn't your default assumption be that the market is close to optimal? Though possibly it's only a psychological advantage -- maybe people prefer longer waits to longer lines.

I think the ideal, if you have the resources, is a hybrid system like the returning customs line at JFK -- a big line with someone making sure there are 2 or 3 people waiting for each agent.

Another theory: It's much easier to fit a line of shoppers with carts into a small area if they're in separate lines. Small area with carts and you get the horribleness that is the airport ticket counter line. Single line without the confined area and you get the never-ending snakey thing (as in the Time Warner Center Whole Foods in NYC) that makes it difficult to actually, you know, shop.

Peter: not only is there "a much greater variation in processing time per customer at a bank or post office than at a supermarket or concession stand", but it's much easier to estimate the variance at the latter.

It's easy to guess roughly how long someone will take in a supermarket. How many items are in the cart? Is it a young man with his wallet in his hand, or an old lady who's far more likely to spend a minute and a half counting out exact change in pennies?

Estimation is more difficult at the Post Office. Even someone with a single letter or package in his hand may want insurance and delivery confirmation and a bunch of stamps of various denominations and maybe some money orders, too.

At the bank, it's impossible. People aren't exactly eager to show how much money they're carrying. The guy in front of you may be a small businessman with 37 checks and $1000+ in small bills to deposit and then want to transfer a bunch of money into and out of various accounts. I've seen some bank customers come in with very little in their hands and still take 20-30 minutes to transact their business.

Mike is right. Queue space is a consideration at groceries and some other outlets such as building supplies.

The customers are the same size but they are pushing carts and sometimes trolleys with large amounts of goods.

The single queue prevents efficient use of space close to the register because only one customer can be near any given register. And customers cannot be unloading goods for checkout.

Observations: Too many in America simply don't wish to be courteous. Once in residence at the register they intend to take their time just as the founding fathers instucted.

Women write checks. Coupons actually delay us very little in comparision. Fair, fat, and forty identifies both diabetic potential and lines to avoid.

Large retailers need a 'takeout' policy. When a cashier sees a customer is likely to cause an inordinate delay that customer is turned over to that takeout manager. The cashier continues with the next customer.

When does the takeout occur? When a customer presents an unsuitable check or plastic. Cannot find identification. Decides he/she forgot something and 'will be back in a minute' or sends the hubby or kid to find it. Wants to argue about expired coupons. Decides a detailed audit of the bill with the cashier is in order. Or the dreaded price check is taking too long.

Large retailers need a 'takeout' policy. When a cashier sees a customer is likely to cause an inordinate delay that customer is turned over to that takeout manager. The cashier continues with the next customer.

By the time the cashier in a supermarket becomes aware of a potential delay, the customer in question is likely to have much of his or her order unloaded on the belt. As might the next customer.

Fair, fat, and forty identifies both diabetic potential and lines to avoid.

Not to be nitpicky or anything, but diabetes rates actually are much higher among non-whites, in other words people who are not fair.

Fat, forty, female, full of gas - noted factors for gallstones.

As Apu pointed out to Marge, the long line consisting solely of men who are shopping alone is still almost certainly your best bet. And the use of checks for any retail purchase under $1000 should be banned.

Here in Northern California, Walgreen's is the worst offender in regards to forming multiple lines - they really, really want you to form separate lines, like the cashiers are on commission or something.

I could imagine a single queue being better for cashiers in a way which would be bad for customers. Imagine a cashier sees a potentially bad customer next in line. They could delay completing their current transaction until some other cashier was burdened with the bad customer. This will slow the whole line down. With multiple queues, the only recourse the cashier has to avoid a bad customer is to go on break.

Hell is being stuck in the grocery line behind a woman with a full shopping cart and a stack of WIC coupons. I think time actually stands still in this situation. Why, why, why, can't they come up with a better system. It's humiliating for those who have to use them and irritating to those of us stuck in line behind them.
RS

Peter:

Fair, fat, and forty was a phrase used years ago - perhaps it still is. Probably in areas where there were few darker skinned people and it made some sense as medical slang. I heard it in Iowa. Some times 'female' was included.

You also wrote:

"By the time the cashier in a supermarket becomes aware of a potential delay, the customer in question is likely to have much of his or her order unloaded on the belt. As might the next customer."

The takeout makes that customer and others aware that behavior has a consequence. They or someone will move their items to another area. Then they must start over with the takeout manager. In general this will impose a delay and inconvenience upon them for imposing a delay upon others. They may think.

I don't understand "As might the next customer." How does the next customer suffer?

My personal peeve is so-called fast checkout lines limited to twenty items, usually accepting coupons, plastic and checks also. It makes a farce of the process.

Currently my local Walmart operates just as above. People with thirty items 'miscount' or 'misunderstand' and use the lines anyway. They may as well, the store shows no concern.

By the time the cashier in a supermarket becomes aware of a potential delay, the customer in question is likely to have much of his or her order unloaded on the belt.

The takeout makes that customer and others aware that behavior has a consequence. They or someone will move their items to another area. Then they must start over with the takeout manager. In general this will impose a delay and inconvenience upon them for imposing a delay upon others. They may think.

More likely, she'll raise holy hell and create a huge disruption, and store workers will have to summon the police.

Score another point for self-checkout -- six stations and one line! Plus, if it gets just a little long, people start going to the cashier lines even when the self-checkout line is still way faster.

"more likely she will raise.."

Well, if she does then sobeit.

A night in jail and $500 fine. Nothing I prefer more for people who raise holy hell when their own petty behavior bites their butt.

A night is jail is known to have effects. Paris Hilton may resume her ways but my guess - only a guess - is she won't drive drunk in CA for a while.

You seem to be arguing that people won't learn from an unhappy experience and so they shouldn't have any.

I have two other things...

one long UniLine, is longer that 50 short lines... if you think about it as a matter of behavior. A long line that moves fast is perceived as taking longer than 10 short lines, because they are short, no matter how long they take. There is also the sweepstakes that happens when choosing a short line and discovering it IS moving fast. "I win!"

From the marketing standpoint, if you have 10 short lines, you can merchandize to each line, because the people will be very close for a time, while a single line will actually move a lot while you are in it...

I saw a story about giving the customer the scanner to use while shopping, and then just paying the cashier when you walk out... and that sounds best to me.

Frankly, I like to choose my attendant to be. Like some of the others, I size up who is doing what. Some are total fumble fingers and even though they may only have 3 people in their line, you very well may 'beat your time' if you go into a line of 5.

Sometimes I just don't like the cut of their jib, and I go to a line where I like the looks of the person. Friendliness matters, and I prefer that over supercilious arrogance with the projected feeling of "I've got the power over you, and you can't do squat about it."

Check writing? WIC coupons?

I feel like I am reading a blog from 1977...

And Falkoyn, I couldn't agree more. I don't know what kind of look-ism I'm guilty of, but teen age boy cashiers are without a doubt the slowest, dumbest, and rudest people to work in retail.

Sorry Jane. A unified queue does not necessarily move checkout traffic faster. The key insight is the parallelizing of unloading activity with checkout activity. People 2 and 3 back in line are unloading while the person in front is being scanned and paying.

If you visit a typical Fry's Electronics, they have a single line, with the distance from the front of the line to a checker quite long on average. This leaves the checkers idle for several seconds. If the person handling the line isn't paying attention, it can also lead to disorganized contention and multiple customers end up assigned to a single checker. And then there's the problem of one really large person getting through the checkout when another is at a checker, or people who aren't swift with their carts.

The grass is not greener. But Mitt Romney is still and asshole. And "Tagg" is a stupid name.

A night in jail and $500 fine. Nothing I prefer more for people who raise holy hell when their own petty behavior bites their butt.
You seem to be arguing that people won't learn from an unhappy experience and so they shouldn't have any.

Store management is not going to want a confrontation with an irate customer in the first place. For any number of reasons.

Also note that a customer who is told to go to the "takeout" line might exercise her disgust simply by walking out of the store and leaving her purchases (which she hasn't paid for, so there's no financial loss) behind at the original checkout. Assuming that much of the stuff is already on the belt, the checkout line will be out of service until store employees can clear it off. They'll also have to return the items to the shelves, especially the perishables.

Diverting troublesome customers to a special takeout line looks good in theory, but isn't going to work well in practice.

So that more items can be placed along and sold in checkout lines.

Jared, the uni is better because you are less likely to have a downtime on one checkout while there is still a backup on others.

It has to do with size/complexity of the transaction. Bank/postoffice transaction are small, shoppers are carrying merchandice which needs more space to be process. The customer is carry a greater load and travel a greater distance the service person, so it make sense to pick a server and queue there.

At my local drugstore, a spontaneous "unified queue" often forms. That never happens at the supermarket next door.

At the drugstore there are only three registers, all pretty close together and easy to see. The way the registers are set up you can't put your purchases "on the counter" until the previous buyer has left.

At the supermarket there are ten registers, spread over a large distance--and there is a large space where you can put your purchases while the previous buyer is still being attended to, so that they are ready to be checked out.

On a different American Blog, I got the impression that you chaps over there don't do self-checkout the way that we chaps over here do. We carry a hand-held scanner around the store, scanning each item as we put it in the cart/trolley. When we've finished, we insert the scanner into a port and our bill is printed out. We check it (if we want to) and pay - usually by chip-and-pin credit card. This highly automated system works a treat.

dearieme -
How do you deter theft in that situation? US self-checks require each item be scanned and then placed in the bagging area for weighing before the next item can be scanned. If you have more than a small handful of items, it's faster to go through a regular checkout.

Devilbunny: the store reserves the right to check your bags before you leave. When I was growing up (in the 50s) Britain was run on the assumption that the vast majority of people are honest - or, at least, middling honest. Nowadays that would seem to be a rash assumption, but the store chain we use in this way ("Waitrose") presumably reckons that it's a good approximation for its customers. Anyway, my wife and I have never been stopped and checked. (Not only do we look angelically honest, but I'm a huge, fierce-looking fellow.)

"Hell is being stuck in the grocery line behind a woman with a full shopping cart and a stack of WIC coupons. I think time actually stands still in this situation. Why, why, why, can't they come up with a better system. It's humiliating for those who have to use them and irritating to those of us stuck in line behind them."

There is a better system. They issue debit cards, which can tap two separate accounts, WIC [1] and other welfare money. On the first of the month, the government transfers money into the accounts. About 5 minutes later, the stores are full of slow, fat people buying TV dinners, snack foods, & soda on the WIC, and cigarettes and booze on the other account. But at least they finish checkout by just scanning the cards.

RS, where do you live that gov't technology is still in the 60's?

[1] For Dearieme and any other non-Americans, WIC is the current name for the main welfare program for feeding the poor. And I'm not kidding about the expensive pre-packaged meals, snacks, and soda. WIC families are often hungry by the end of the month, but if you cook healthy meals from scratch, it's unlikely you spend as much money on food as WIC will provide a poor family of the same size.

Steven Postrel has a nice discussion of this going on at
http://organizationsandmarkets.com/2007/03/28/design-puzzles/

Comment 47 incorporates a good deal of what was said about supermarket lines.

Is queuing theory not a standard part of business curricula? I had a chapter on it (customer arrivals follow a Poisson distribution, service times follow a negative exponential distribution) in a required Operations Management class and figured everyone did. I was surprised this seems like such an unsolved problem (or such an erroneously solved problem) for so many people.

JSinger:

This discussion isn't about whether queues are understood or whether operations research has been forgotten by every mind but yours.

Jane asked a question and didn't give many facts. Reponses discussed why a single queue is better only in some places. Responses also drifted into what frustrates people in separate queues and how that might be handled.

One key answer is the unloading of items at the register.

Foot traffic patterns don't much concern theory but they do determine if people can easily move from one side of the store to the other. A long queue can complicate that.

Another is simply that stores believe individual queues increase impulse sales of high margin items. That probably has little to do with Poisson. It didn't in my MBA studies.

And some people just want the freedom, rational or not, to bet on the fastest line or choose the cashier. I imagine that impulse varies widely among cultures and around the world.

I suspect Operations Management would tell us that eliminating registers is the answer. Just let people take what they want home, total it up, and pay onlne or by mail when convenient.

But then the prices would need to be on each item. And marking is expensive. Drat! Double Drat!

If a store has two or more exits a sufficent distance apart then the wait time saved using a single queue model needs to be balanced against the necessity to use a register that might be on the opposite side of the store from the desired exit.

While there might not be a significant time saving (and you might argue that the extra walking would be good for most people), there's always the possibility that the next person in line will adamantly wait for a more convenient register to become available and negate any time saved over using multiple queues.

The same principle might also apply to widely spaced registers even if there is a single exit.

K- heh, double drat... so we go back to having stockers with pricing guns, like the olden days? Everything old is new again... actually I know someone from the UK mentioned that they are doing experiments with hand-scanners [I seem to recall the buggy itself doing the total by RFID while you are shopping being experimented with also], and simply handing your payment to the cashier on the way out... and that'll cover all the bases

On the other hand this may just be a riff on how everyone grumbles about long check out lines, but never get angry enough to punish that economically. Mostly because what-re-you-gonna-do? EVERY Store you go to, has the same problem... 40 checkout lanes, and 2 cashiers...

D

RS, where do you live that gov't technology is still in the 60's?

Right smack in the middle of Silicon Valley: San Jose CA. I've heard about these cards and even see special card readers for them in many stores yet for some reason whenever I'm at my local Albertsons I get stuck behind someone with a handful of WIC coupons. I don't get it.

RS - your first mistake is going to Albertson's. Lucky's wasn't bad, and it had low prices. Ever since Albertson's bought them, they raised the prices to higher than Safeway's, dropped the "three's a crowd" policy, and let the service slip to even worse than Safeway's.

There is something called EBT, which is basically an ATM card for welfare, but I think it's still voluntary, so people who can't handle the complexity of ATM/EBT transactions still get the coupons.

I have trouble at self-checkouts at Home Despot, probably because the scale at the bag doesn't work right. I'm not the only one - the self-checkout barely saves any time, between bagging issues and the inexperience of customers slowing them down. Most customers aren't trained cashiers, which means that some parts of the process will be slower without a cashier.

Yes, self-checkout isn't to save customer time, but to save the only kind of time the store directly pays for - that of hourly employees. It can sometimes save customers time, too, but that's because all the self-checkouts are operating all the time, when before you might find 20 checkout lanes and only 5 clerks, so the lines are much, much shorter.

A small grocery store could use a hybrid uni and multi model, if they had the space: keep customers in a single line until a space opens up for the one at the head of the line to start unloading the cart onto a conveyor belt. So you'd have one long line feeding many short lines. To make this work would require rearranging the part of the store in front of the registers. They could still sell candy and magazines to the people waiting in line, by relocating those racks to define the serpentine single line.

Two problems. One is that it would initially confuse the customers, but if people can figure out I-pods and cell-phones, they'll get this system pretty soon. The bigger problem is, most stores have a dozen or more registers. Go into a supermarket at 8:00 am (say), when there are virtually no customers, and try to find a point at which you can see all the registers. How is the customer at the head of the uni-line going to know when a register is opening up? A uni-line works even at large banks because they put the teller stations in a U enclosing what looks like a half acre of space, and they keep that space clear so the person at the head of the line is standing just inside the U with a view all around it. Banks can waste space like this - it's conspicuous consumption proclaiming, "We've got the money." Grocers operate on far too narrow a margin to afford wasted space.

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