Let Game Theory Tell You When It’s Time to Go Shopping | Hacker News Reader

Let Game Theory Tell You When It’s Time to Go Shopping

nautil.us

49 pointsdnetesn29 comments

Pre-Covid, a good trick for the non-religious or non-Christian person who lived in areas of the South with regular church attendees was to go early Sunday morning, when people were at religious services. The only issue was if you wanted to pick up alcohol and you lived in areas with blue laws, you'd be stymied since you were shopping before noon.

Might still work now if churches are hosting regular web-based worship, but I don't know.

You would think there should be some sort of reward in the form of saved time from going to the supermarket at an unpopular time. But my closest supermarket changes the staffing levels at checkout to coincide with the level of shoppers. So, I spend the same amount of time in line no matter when I go.

Lots of grocery stores in the US have a bunch of self checkout lanes and only 2-3 cashier lanes. Walmart, target, Kroger, Lowe's Foods, etc.

It does help if you go when there's low traffic.

Where I live (Seattle), a portion of the self-checkout lanes are also closed to coincide with the level of shoppers. I was told that this is because of labor unions - basically it guarantees work for the cashiers.

I've never successfully used self-checkout at a grocery store without triggering the anti-theft mechanisms. I used to have this problem at CVS but I'm pretty sure they've disabled the scales in recent years. Likewise for Target--scales disabled. I assume grocery store theft is more common, or perhaps their margins too slim, to disable the measures.

One more factor I would recommend to take into account is when the store restocks.

For where I live, the supermarket I usually go to always restocks Tuesday mornings, sometimes on Thursday mornings.

This may be a bit selfish, but I always go on Tuesday morning 10AM and it has not been crowded do far, and I've had zero issues with needing repeated trips due to groceries being out of stock.

EDIT: One would expect it to be busier right after / during restocking, but that has not been the case at all. Maybe the supermarket has an incentive to restock during the least busy times or people have not caught on in general yet.

Talking to people working in retail I keep hearing the same thing:

People are bored. Often see the same people coming in several times a week, buying random stuff and browsing the shelves. Standing in line outside stores for 30 minutes just to buy a few knickknacks.

You don't seem to understand how much I need those biscuits. And I need them now!

I was a retail manager for 6 years while I finished grad school and post doc work. It was eye opening for me.

Many, many of the elderly people who came to the store were there almost every day, and were there just for the human interaction.

It genuinely made me sad that there wasn't a better outlet, or an outlet that wasn't based on the consumption of nonsense goods.

Worked retail (managed eyeglass lab) to pay for my eng deg. Can confirm. There were a few regulars I grew fond of.

Even if there were a local place or activity for socializing, going to a retail store during the day is a good move. Clerks won't have many people competing for their attention and the clerk-customer roles make it easy to break the ice. The clerk will realize this isn't a sales discussion but is probably happy to shoot the breeze, anyway. Shopping at a store gives a very nice framework for casual conversation.

Maybe grocery stores should start social events and advertise them to regular customers.

We're they spending a lot on junk?

It's fair to have a small "fee" for hosting. And if they are buying food things and then giving them away, that's two social interactions!

When I skipped school in the 80s, I'd get to the mall before it opened for business and watch as they opened the doors early for "mall walkers" -- old people who were there for exercise sheltered from the Florida heat and humidity.

That's my father since he retired. He does wood working as a hobby, but he will use any excuse to go to the hardware store. I don't know his actual frequency, but I wouldn't be surprised if he is there 4-5 times a week, with or without a project lined up.

Grab a Coke, walk around Home Depot... I do enjoy!

Considering that most people in the UK get up late and prefer to queue up around noon or in the evening/afternoon you don't need any maths to figure out that you just need to go when the store opens. So far going between 6am and 8am has been successful for me.

I think that depends on where you live, my local supermarket is quietest at 11am, and there’s a queue at 8am.

I've found going right after lunch hours during the "work week". Basically 2-3pm on Tue/Wed has been the sweet spot for me. Store is restocked after weekend and folks are not there during their lunch time.

This. You can do the game theory alright, but statistically speaking there are many more people who are constrained by their working hours to go to the shop during either lunchtime (12:00-13:00) or just after 18:00.

This has been my strategy too and so far has been working well

In general I agree, but this has been complicated here the last few months due to Covid-19. Stores have both limited hours and developed senior only hours. There were also sometimes people queueing up early to buy “scarce” goods like TP when the store opens. If you go to a store at open you might get turned away, find the store doesn’t open at the posted hours, or find a small crowd.

I’ve been going around 11 these months. Stores are open. Senior hours are over. Working people aren’t on lunch yet. Non-working people have generally not gotten out. And usually I see employees restocking goods.

From what I understand, this is arguing that we should be collectively doing this in order to limit overcrowding, this method is not very helpful as an individual. If based on past trends it is overcapacity at 2:00 and under capacity at 4:00, as and individual you shouldn't expect that to change and should always go at 4:00.

Without a prescription for how many people want to go at a given time, you can't really make use of this information. If every body was following this rule, there ought to never be overcrowding, so you could never know this information by using past data. So you would need to use a sign up or polling method to figure out. If using a sign up, you could just set a cap on how many people can sign up so you don't need randomness. If using polling then this method could be helpful.

Though another issue with this model is assuming a fixed positive utility from going when overcrowded and a fixed negative utility when overcrowded. In reality the fewer people the higher utility, plus each individual has different utility based on what time they are going. Taking all this into account, I feel like the only reasonable approach is what is already done, go to the store during a convenient time for you that is the least busy based on passed data. If everyone does this, we should expected to reach a happy equilibrium (sans unexpected upsets, such as the recent rushes before lock downs).

If there is positive utility from shopping while crowded, it means the game is Prisoner's Dilemma: going shopping will be always the best option. I can understand why they didn't consider that possibility as it is "unsolvable" anyway.

> I feel like the only reasonable approach is what is already done, go to the store during a convenient time for you that is the least busy based on passed data.

But people don't have good data--you'd have to go at random times for weeks or months to have a sense of the best times. And in any event people don't invest much effort in this. We're not rational beings. We systematically underestimate the value of collecting and applying such data, just as we systematically overestimate the value of other things. Not to mention the collective action problem in maximizing total social benefit.

Supermarkets need to lower the cost of information aggregation. They could prominently display at the entrance and at checkout lanes a simple graph of customer traffic so that people could instantly, freely know how to avoid the crowds. But this might have to be mandated by law as they otherwise have very little perceived incentive to do this. Even though the cost is trivial, businesses aren't perfectly rational actors any more than humans are. Anyhow, trivial isn't zero, especially when the returns are uncertain. It will take a significant external push to move away from their local optimum solution--managing crowds by adjusting the number of cashiers.

Google will report how busy some business are on an hour by hour basis, I assume based on anonymous phone locations collected. If google covers the business you want to go to that would solve the coordination problem.

I'm not sure how to make google show this information. Usually I can just look up "[business] hours" and it will give me the plot, it might not be showing that information right now due to low activity because of the lock down.

Using a job market matching model would be more appropriate for this, seeing that each hour is associated with an convenience level (a la wages) and disutility from crowding.

However economics is about studying equilibria, not finding recipes for what to do. Just check Google Maps for crowding levels if you need to go to the supermarket, or request a queue status indicator to be put into the market's website.

I kind of missed on what was solved when he switched to a text description.

Expect airborne virus to follow Google Maps 'busy time' graphs, and surface virus to be the exponentially weighed integrated busy time. Be careful around people that appear to be suffocating. No need for maths or game theory, just common sense.

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