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コストコのホットドッグが値上がり

原題: The price of a Costco hot dog has gone up

costcohot dogshrinkflationinflationphotogrammetryconsumer price indexbeef pricesvolume analysis
原文 ↗

日本語訳

# コストコのホットドッグの価格は上がっている

コストコは、オールビーフのクォーターポンド・ホットドッグとバンズ、そしてコーラなどの飲み物の無料おかわり付きを1.50ドルで販売している。この価格は1984年から変わっていない。この価格設定は神聖なものとされており、コストコの共同創設者ジム・シネガルは、当時のCEOクレイグ・ジェレネックに対し、もし値上げしたら殺すとまで言ったという(Today紙より)。

米国では多くの支出カテゴリーで価格が上昇している中、コストコはその約束を守っているのだろうか? 私は3年の間隔を空けて、同じコストコでホットドッグを2回購入した。どちらも価格は約束通り1.50ドルだった。しかし、2回目のバンズは小さく見えた。これは、「もし3年間ラベルの価格が変わっていないのであれば、私はより少ない量のホットドッグに対して同じ金額を支払っていることになるのだろうか?」という疑問を抱かせるに十分な違いだった。

### ソーセージが定規になる

幸いにも、私は両方のホットドッグを撮影していた(図1)ため、原理的にはバンズのサイズの差を測定することができた。しかし、2枚の写真は距離も角度も異なり、さらに重要なことに、定規も使っていなかった。だが幸いなことに、定規は必要なかった。ソーセージが定規になるからだ。

私はソーセージの長さを8インチ(一定)と見なし、これを既知の長さとして2枚の画像を位置合わせ(レジストレーション)するために使用した。まず、各ソーセージの両端を特定した。次に、カメラの焦点距離とソーセージの直径を1インチと仮定して、各ソーセージがカメラに向かってどの程度傾いているかを推定した。単純なピンホールカメラモデルによる適合の結果、2023年のホットドッグは約13度画像平面から傾いており、2026年のものはほぼ真横を向いていることがわかった。その後、画像を8インチの基準線に合わせて回転・スケーリングし、遠近法による誤差を補正した。

### バンズが小さくなっている

コストコのホットドッグバンズは、2つの半分に分けて、長さが約0.8インチ、合計の幅が0.87インチ減少していた。バンズの総体積の減少を推定するため、バンズを2つの直方体(角度補正後の長さ × 平均可視幅 × 一定の2インチの奥行き)としてモデル化した。(注:2026年の写真ではソーセージがバンズの半分を一部隠しているため、この推定値はわずかに過大評価されている可能性がある。)

表1:位置合わせされた画像から推定された、角度補正済みのバンズ半分の寸法。数値は表示用に丸められている。面積、体積、価格は丸め前の値から算出している。

この2つの直方体モデルに基づくと、バンズの体積は29.5立方インチから16.1立方インチへと、45%減少していた。言い換えれば、2026年のバンズは2023年の約半分のサイズである。そして、ソーセージ自体は変わっていないため、直径1インチ、長さ8インチの円柱としてモデル化した($V = \pi \times (0.5\text{ in})^2 \times 8\text{ in}$)。その体積は約6.3立方インチとなり、これを用いて一食分の総体積を推定した(表2)。

表2:推定されたホットドッグの体積と立方インチあたりの価格。

この推定によれば、1.50ドルのホットドッグに含まれる体積は、2023年と比較して20

原文(英語)を表示

The price of a Costco hot dog has gone up

Costco sells an all-beef quarter-pound hot dog and bun, with free refills on Coke products, for $1.50. The price has not changed since 1984. This price point is so sacred that Costco co-founder Jim Sinegal reportedly told then-CEO Craig Jelinek that he would kill him if he ever raised it (Today).

As prices have gone up in the US across multiple spending categories, has Costco kept that promise? I bought two hot dogs at the same Costco three years apart. Both times the price was $1.50, exactly as promised. But the second hot dog bun looked smaller, enough so to raise the question: if the sticker price has not moved in three years, am I paying the same amount for less hot dog?

The sausage is the ruler

Conveniently, I had photographed both hot dogs (Figure 1) so I could, in principle, measure the size difference of the bun. But the two photos were taken from different distances, at different angles, and—importantly—without a ruler. But, luckily, I didn't need one because the sausage is the ruler.

I treated the sausage as unchanged at 8 inches long, giving me a known length I could use to register the two images. I first located the two ends of each sausage. I then used the camera focal length and the dog's assumed 1-inch diameter to estimate how far each sausage pointed toward the camera. A simple pinhole-camera fit put the 2023 dog at about 13 degrees out of the image plane and the 2026 dog nearly broadside. I then rotated and scaled the images to the same 8-inch reference line while correcting the measurements for perspective.*

The buns are smaller

The Costco hot dog bun lost about 0.8 inches of length and 0.87 inches of combined width across its two halves. I modelled the bun as two rectangular prisms (angle-corrected length x mean visible width x a constant 2-inch depth) to estimate the total volume loss. (Note the sausage partly hides one bun half in the 2026 photo, so this estimate may be slightly overstated.)

Table 1: Angle-corrected bun-half dimensions estimated from the registered images. Measurements are rounded for display; areas, volumes, and prices were calculated from the unrounded values.

Under this two-prism model, the bun volume dropped from 29.5 cubic inches to 16.1 cubic inches—a reduction of 45%. Put another way, the 2026 bun is about half the size of the 2023 bun. And since the dog itself was unchanged, I modeled it as an 8-inch cylinder with a 1-inch diameter: V = pi x (0.5 in)^2 x 8 in which is approximately 6.3 cubic inches to estimate the volume of the full serving (Table 2).

Table 2: Estimated hot dog volume and price per cubic inch.

By this estimate, the $1.50 hot dog contains about 37% less volume in 2026 than it did three years ago, in 2023. While the price is the same, the nominal cost per cubic inch has increased by about 60%.

So, to my dismay, the price of a Costco hot dog did go up.

Bamboozled by the bun

How did we get here? It's likely that Costco changed bun suppliers or asked its original supplier to make a smaller bun. While Costco does not publish its food-court bun contracts, it does offer product listings for those same buns. A now-unavailable Costco listing for Francisco International hot dog buns shows a 28-ounce package containing 12 rolls, or 2.33 ounces per bun. (I suspect this is the original bun, or one similar to it.)

The new alternatives currently listed by Costco weigh less. Francisco International deli hot dog buns come in a 26.6-ounce package containing 16 rolls, or 1.66 ounces per bun. (The Francisco International product image, incidentally, looks weirdly AI-generated.) Franz Classic hot dog buns come in a 42-ounce package containing 24 rolls, or 1.75 ounces per bun.

That is 25–29% less bun by weight. Even though weight and volume are not interchangeable, both measurements tell the same story as the photogrammetry analysis above: less bun.

The Bureau of Labor Statistics average-price data show the retail price of white pan bread falling from $1.97 per pound in August 2023 to $1.82 per pound in July 2026—a decrease of about 8%. Somehow, the bun shrank while bread got cheaper. I had been bamboozled by the bun.

Beaten by the beef

Changing beef prices may explain why Costco went after the bun. Bureau of Labor Statistics data show ground beef rising from $5.08 per pound in August 2023 to $6.89 per pound in July 2026, a 36% increase, or about 45 cents more for a quarter pound at retail prices. Costco may have taken it out of the bun. In other words, the buns were beaten by the beef.

Inflation does not save Craig Jelinek

Beef got more expensive and bread got cheaper. Those cost pressures may explain why Costco changed its buns. But they do not tell us whether the $1.50 meal is still the same value. For that, I compared the August 2023 Consumer Price Index (CPI-U) with the most recent July 2026 index.

The August 2023 CPI-U all-items index was 307.026; the July 2026 index was 333.918. That is an inflation factor of 1.0876, meaning $1.50 in 2023 is equivalent to $1.63 in 2026 dollars. The source data are available from the Bureau of Labor Statistics' August 2023 CPI release and July 2026 CPI files.

The fixed $1.50 price saved customers 13 cents relative to inflation. But the serving size shrank by 37% (while the purchasing power of $1.50 fell by only about 8%). In 2026 dollars, the 2023 hot dog cost 4.56 cents per cubic inch; the 2026 hot dog costs 6.69 cents per cubic inch. Inflation lowers the unit-price increase from 60% nominal to 47% real.

Therefore, at the 2026 rate of 6.69 cents per cubic inch, the old 35.8-cubic-inch serving would cost about $2.40 (77 cents more than its inflation-adjusted 2023 price of $1.63.) That is shrinkflation.

So, Mr. Sinegal, a Costco hot dog has effectively gone up by 77 cents in three years. I'm sure you're a man who keeps your word, but please don't kill Craig Jelinek. Just ask Ron Vachris to give us back the old bun. Thank you.

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