Market Share Competition in the Japanese Gasoline Market: A Two-Stage Game Approach

The Great Gas Station Game: Who Sets the Price at the Pump?

Imagine you are trying to figure out why the price of a slice of pizza changes from one neighborhood to another, even though the ingredients cost the same everywhere. This is the kind of puzzle that economists love to solve. They study markets, which are just fancy words for places where buyers and sellers meet. In this specific story, we are looking at the Japanese gasoline market, a place where big oil companies (refiners) make the fuel, and thousands of small gas stations sell it to you.

To understand this paper, you need to know about two famous ways companies compete. The first is called Cournot competition, named after a French economist. Imagine two bakers deciding how many loaves of bread to bake before they know what price they will sell them for. They guess how much their rival will bake, and that guess determines how much bread is left over, which sets the price. The second is Bertrand competition, named after another economist. This is like two bakers who have already baked their bread and are now standing in the shop, screaming prices at each other to see who can sell the most. If one baker lowers their price even a tiny bit, they steal all the customers. This paper combines these two ideas into a "two-stage game," asking: What happens if the big companies decide how many gas stations to open first (like the bakers deciding how many loaves), and then those stations fight over prices later?

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The Paper: A Two-Act Play in the Japanese Gas Market

This paper, titled "Market Share Competition in the Japanese Gasoline Market: A Two-Stage Game Approach" by Keiichi Kawamura, dives into the chaotic world of Japanese gas stations to see how they actually set prices. The author suggests that the market isn't just a free-for-all; it's a carefully choreographed dance with two distinct steps.

Act 1: The Big Bosses Decide the Stage (The Refiners)
First, the paper imagines the big oil companies (the refiners) as the directors of a play. They don't just set the price of the fuel; they decide how many gas stations to open or keep open. The author calls this Cournot competition. Think of it like two giant pizza chains deciding how many new locations to build in a city. They don't set the price of a slice yet; they just decide, "We will open 500 stations, and you open 400." The paper argues that these companies use the number of gas stations as a proxy for their power. If a company has more stations, it has more "capacity" to sell fuel.

Act 2: The Local Shops Fight for Customers (The Retailers)
Once the stations are open, the second act begins. The gas stations (retailers) are now in a Bertrand competition. This is the "price war" phase. If you have a gas station right next to another one, and you both sell the exact same fuel, you have to lower your price to get people to stop at your pump. The paper suggests that in areas where two different brands are right next to each other, the price drops to the bare minimum (the wholesale cost). But in areas where a station is the only game in town (a monopoly), that station can charge a higher price because you have no other choice.

The Big Discovery: It's All About Concentration
The author built a mathematical model to predict what would happen in this two-stage game. Then, they tested it against real data from 1999 to 2022, covering all 47 prefectures in Japan. They looked at how the price of crude oil, the number of gas stations, and how "concentrated" the market was (meaning, how much of the market is controlled by the top four companies) affected the price you pay at the pump.

Here is what the data actually showed:

1. Crude Oil Matters: When the price of crude oil goes up, the price of gasoline at the station goes up, too. The study found that for every 1 yen/liter increase in crude oil prices, the retail price went up by about 1.33 yen/liter (in one model) or 1.19 yen/liter (in another).
2. Fewer Competitors Mean Higher Prices: This is the most important finding. The paper suggests that when the market is "concentrated"—meaning the top four firms control a larger share of the gas stations—the prices go up. Specifically, if the market share of the top four firms increases by 10 percentage points (a jump from, say, 70% to 80%), the retail price jumps by 6.25 yen/liter.
3. The "Concentration" Brake: There is a twist. When the market is very concentrated, the effect of rising oil prices on the final pump price actually gets a little weaker. The interaction between oil prices and market concentration had a negative effect, reducing the price by about 0.05 yen/liter for a 0.1 increase in the interaction term.

What the Paper Rules Out
The paper explicitly argues against the idea that the Japanese gas market is a simple, perfectly competitive free-for-all where prices are always driven down to the lowest possible cost. Instead, the results suggest that the market structure (who owns the stations) plays a huge role. It also rules out the idea that deregulation (removing government rules) led to a chaotic mess; instead, it suggests the market settled into a predictable pattern of oligopoly (a few big players) that fits the "two-stage game" model perfectly.

How Sure Are They?
The author is quite confident in their findings. They ran statistical tests on data from 1,128 observations (47 prefectures over 24 years). The results were "statistically significant at the 1% level," which is a very high bar for certainty in science. The models explained about 92% of the changes in gas prices (R-squared values of 0.924 and 0.927), which is a very strong fit.

The Takeaway
In simple terms, this paper tells us that the price of gas in Japan isn't just about how much oil costs. It's also about how many gas stations are out there and who owns them. If a few big companies own most of the stations, they can keep prices higher, even if oil prices drop a little. The market acts like a two-step dance: first, the big bosses decide how many stations to build, and then those stations fight over prices, but the outcome of that fight depends heavily on how crowded the dance floor is. The study suggests that after the government stopped controlling the market in the late 90s, the industry naturally evolved into this specific type of competition, where the number of stations and the concentration of ownership are the real keys to the price you see on the pump.