The gallon of milk in a Columbus, Ohio grocery store costs $4.19 this week. It cost $3.61 eight weeks ago. The store hasn’t changed. The cows haven’t changed. What changed is a body of water twenty-one miles wide at its narrowest point, on the other side of the planet.
Here is how that works.
Start at the source. The Persian Gulf sits between the Arabian Peninsula and Iran — a shallow, warm sea roughly the size of Montana. Beneath its floor and along its shores lies approximately thirty percent of the world’s proven oil reserves. Saudi Arabia, Iraq, Kuwait, the UAE, and Qatar pump crude from this region continuously. On an ordinary day, between seventeen and twenty million barrels of oil leave this body of water every twenty-four hours.
They leave through one exit: the Strait of Hormuz.
The Strait is the narrow passage between the tip of Oman and the coast of Iran. At its tightest, it is twenty-one miles wide — about the distance from downtown Chicago to O’Hare Airport. The navigable shipping lanes within it are narrower still: two lanes in, two lanes out, each roughly two miles wide. Every supertanker leaving the Persian Gulf must pass through this corridor. There is no other way out.
Follow one of those tankers. A very large crude carrier — the standard vessel for this route — is roughly a quarter-mile long and carries about two million barrels of oil. It clears the Strait and enters the Gulf of Oman, then the Arabian Sea. It rounds the Indian subcontinent or heads west around the Arabian Peninsula depending on its destination. A tanker bound for the United States Gulf Coast travels roughly twelve thousand miles, taking three to four weeks.
It arrives at a Louisiana offshore terminal or a Texas port. The crude is offloaded into pipeline systems that move it inland to refineries in Houston, Port Arthur, or Baton Rouge. At the refinery, crude oil is separated into its components through a process called fractional distillation — the hydrocarbon chains of different lengths separating at different temperatures. Gasoline comes out. Diesel comes out. Jet fuel, heating oil, petrochemical feedstocks come out.
The gasoline moves by pipeline to a regional distribution terminal in Ohio. A tanker truck picks it up and drives it to the gas station on Route 40 where you fill up on the way to work.
The petrochemical feedstocks go elsewhere — to plants that make fertilizer. The fertilizer goes to farms. The farms grow corn. The corn feeds the cows. The cows produce milk. The milk costs $4.19.
When the Strait of Hormuz is closed or threatened, none of the physical infrastructure changes. The pipelines still run. The refineries still operate. The farms still exist. What changes is the price signal that runs through the entire system.
Oil markets are global and they price in expectation, not just reality. When traders believe supply from the Persian Gulf will be constrained — whether for a day, a week, or a month — they bid up the price of oil immediately. That price increase moves through the refinery margin, through the distribution chain, and appears at the gas station within days. It takes somewhat longer to reach grocery prices, because food supply chains have more insulation, but it arrives there too.
The gallon of milk is more expensive not because less milk was produced. It is more expensive because the energy required to run every step of its production and distribution became more expensive, and because every company in that chain passed the increase forward.
This mechanism is not new. The historical record on Strait of Hormuz disruptions is instructive precisely because it shows both how quickly prices respond and how reliably they recover.
The 1973 Arab oil embargo — technically a different route, but the same mechanism — quadrupled oil prices within months and produced gasoline shortages across the United States. It resolved within a year. The 1979 Iranian Revolution removed Iranian production from the market and sent prices to levels that, adjusted for inflation, haven’t been reached since. It resolved within two years. The 1990 Gulf War briefly threatened Gulf shipping; markets spiked and recovered within months once the outcome became clear. In 2019, Iranian attacks on Gulf tankers sent brief price spikes that dissipated within weeks.
The pattern in each case: rapid price increase, period of elevated prices while the disruption persists, recovery once the situation resolves. The duration of the elevated period has correlated closely with the duration of the actual supply disruption, not with the severity of the initial spike.
The twenty-one-mile strait and the gallon of milk in Columbus are connected by twelve thousand miles of ocean, several weeks of transit, a refinery, a pipeline, a fertilizer plant, a farm, and a truck. That connection is invisible under ordinary circumstances. It becomes visible when something interrupts the flow.
Understanding the mechanism doesn’t make the price increase less real. But it does make the situation more legible — and legibility is the beginning of calm. The infrastructure that connects the Persian Gulf to Ohio is old, well-mapped, and has been interrupted before. Each time, it has found its way back to function.
The milk will cost $4.19 for a while. Then, in all likelihood, it won’t.
