Why do competitors open their stores next to one another? - Jac de Haan

為什麼競爭者愛把店面開在另一家旁邊？ - Jac de Haan

Translator: tom carter Reviewer: Bedirhan Cinar

譯者: Jephian Lin 審譯者: Hao-Wei Chang

Why are gas stations always built right next to other gas stations?

為什麼加油站總是建在另一家的旁邊？

Why can I drive for a mile without finding a coffee shop

為什麼我會開了一哩路 都沒見到咖啡店

and then stumble across three on the same corner?

卻在同一個街角一次撞見三家呢？

Why do grocery stores, auto repair shops and restaurants

為什麼雜貨店、汽車行、還有餐廳

always seem to exist in groups

似乎總是成群地出現 而不是在整個社區中平均分佈呢？

instead of being spread evenly throughout a community?

While there are several factors

儘管要決定在哪開店 要考慮許多因素，

that might go into deciding where to place your business,

類似的店家會成群出現 可以用一個很簡單的故事來解釋，

clusters of similar companies can be explained by a very simple story

called Hotelling's Model of Spatial Competition.

那就是「空間競爭的霍特林模型」。

Imagine that you sell ice cream at the beach.

想像你打算在沙灘上賣冰棒。

Your beach is one mile long and you have no competition.

這沙灘有一哩長，而且沒有競爭者。

Where would you place your cart in order to sell the most product?

為了賣出最多的冰棒， 你會把你的推車放在哪？

In the middle.

正中間。

The one-half-mile walk may be too far for some people

半哩對於某些 在沙灘盡頭的人或許太遠了，

at each end of the beach,

但是你的推車已經 盡可能地服務最多的人了。

but your cart serves as many people as possible.

有天你去工作的時候， 恰巧遇到你親戚 Teddy 也推著冰棒車去沙灘。

One day you show up at work

just as your cousin Teddy is arriving at the beach

事實上，他賣的東西跟你完全一樣。

with his own ice cream cart.

In fact, he's selling

exactly the same type of ice cream as you are.

你們達成協議， 把海灘分成兩半。

You agree that you will split the beach in half.

In order to ensure that customers don't have to walk too far

為了讓客人們不用走太遠

you set up your cart a quarter mile south of the beach center,

你將推車停在 中間往南 1/4 哩的地方，

right in the middle of your territory.

也就是你地盤的正中間。

Teddy sets up a quarter mile north of the center,

Teddy 則停在中間往北 1/4 哩的地方，

in the middle of Teddy territory.

也是他地盤的中間。

With this agreement, everyone south of you buys ice cream from you.

有了這個協議，每個比你更南方的客人 會來買你的冰棒。

Everyone north of Teddy buys from him, and the 50% of beachgoers in between

每個比 Teddy 更北方的客人會去買他的， 而你們之間的遊客

walk to the closest cart.

會走向最接近的推車。沒有人會走超過 1/4 哩，

No one walks more than a quarter of a mile,

and both vendors sell to half of the beachgoers.

而且兩個冰棒攤有等量的客源。

Game theorists consider this a socially optimal solution.

賽局論專家認為 這是一個對全社會最佳的結果。

It minimizes the maximum number of steps any visitor must take

因為它縮短了 最遠的遊客來買冰棒的距離。

in order to reach an ice cream cart.

因為它縮短了 最遠的遊客來買冰棒的距離。

The next day, when you arrive at work,

隔天，你來工作，

Teddy has set up his cart in the middle of the beach.

Teddy 已經把他的推車 停好在沙灘的正中間。

You return to your location a quarter mile south of center

你一樣到那南方 1/4 哩的地方

and get the 25% of customers to the south of you.

然後得到那些 25% 比你更南方的客戶。

Teddy still gets all of the customers north in Teddy territory,

而 Teddy 依舊得到 整個他北方地盤的客戶，

but now you split the 25% of people in between the two carts.

但是現在你們必須對分 你們中間那 25% 的客源。

Day three of the ice cream wars, you get to the beach early,

冰棒戰爭的第三天，你提早到了沙灘，

and set up right in the center of Teddy territory,

然後直接在 Teddy 地盤的正中間設攤，

assuming you'll serve the 75% of beachgoers to your south,

期待你可以得到你南方的那 75% 客戶，

leaving your cousin to sell to the 25% of customers to the north.

然後把北方那 25% 的客戶留給你的好兄弟。

When Teddy arrives, he sets up just south of you

Teddy 到的時候， 他在你南方一點點設攤

stealing all of the southerly customers,

偷走所有南方的客源， 然後把你和剩的一小群客源留在北方。

and leaving you with a small group of people to the north.

為了不想被超越，你比 Teddy 更往南十步， 重新得到你的客源。

Not to be outdone, you move 10 paces south of Teddy to regain your customers.

When you take a mid-day break, Teddy shuffles 10 paces south of you,

而當你在中午小憩片刻時， Teddy 又移到你南走十步，

and again, steals back all the customers to the far end of the beach.

再一次地，偷走所有南方大部份的客源。

Throughout the course of the day,

一整天下來，你們雙方不斷地、 規律地往南移動，

both of you continue to periodically move south

towards the bulk of the ice cream buyers,

來得到大量的冰棒買家，

until both of you eventually end up at the center of the beach,

直到雙方都到了沙灘中間，

back to back, each serving 50% of the ice-cream-hungry beachgoers.

背對背，每個人各為 50% 那渴望冰棒的客戶服務。

At this point, you and your competitive cousin

到這個地步，你和你那愛好競爭的兄弟 已經達到了賽局論專家所稱的「納許平衝」──

have reached what game theorists call a Nash Equilibrium -

the point where neither of you can improve your position

也就是雙方都無法藉由 調整現行策略來改善設攤地點

by deviating from your current strategy.

Your original strategy,

你們各據南北 1/4 哩地方的原始策略

where you were each a quarter mile from the middle of the beach,

並不會持久，因為它並不是納許平衡。

didn't last, because it wasn't a Nash Equilibrium.

Either of you could move your cart towards the other to sell more ice cream.

你們雙方都可以把車子前中間移一點， 好賣更多的冰棒。

With both of you now in the center of the beach,

現在你們兩個都在沙灘的中間，

你們都沒辦法再改變位置 來接近遠方的客人

you can't reposition your cart closer to your furthest customers

without making your current customers worse off.

又同時不失去現有的客戶。

However, you no longer have a socially optimal solution,

然而，你們就不再擁有對全社會最佳的結果，

since customers at either end of the beach

因為在沙灘盡頭的客戶

have to walk further than necessary to get a sweet treat.

必須為了冰棒走地比原來更遠。

Think about all the fast food chains,

想想所有的速食連鎖店、服飾精品店、 或是購物廣場的手機販售門市。

clothing boutiques, or mobile phone kiosks at the mall.

Customers may be better served

平均的店家分佈可以 提供客戶更好的服務，

by distributing services throughout a community,

but this leaves businesses vulnerable to aggressive competition.

但是這樣會讓那些 好鬥的競爭者有機可趁。

In the real world, customers come from more than one direction,

在真實世界裡，客戶來自四面八方，

and businesses are free to compete with marketing strategies,

但是生意是各種 市場策略的自由競爭，

by differentiating their product line, and with price cuts,

像是銷售不同的產品，或是提供折扣，

但是各種策略的中心思想， 就是各公司認為和競爭者愈靠近愈好。

but at the heart of their strategy,

companies like to keep their competition as close as possible.

但是各種策略的中心思想， 就是各公司認為和競爭者愈靠近愈好。