That is a lot of milk. New Zealand is one of the world’s largest milk producers, according to IFCN Dairy Research Center in Germany, but it is the largest exporter of dairy products. Some dairy economists doubt that the world’s cows are up to the task and say there is a possibility that the shortage of milk now being seen in parts of the world will spread.

Image Cows in the milking shed of a farm in New Zealand. In many of the worlds emerging economies, milk is the mark of new money, a significant source of protein in an affluent persons diet. Credit... Victoria Birkinshaw for The New York Times

Others say there are plenty of places where more milk can be produced if the price is right. One thing they agree on is that milk prices are likely to stay high and rise even higher.

“No one forecast this rapid shortage of milk,” said Torsten Hemme, head of the IFCN center.

This is not good if you are in the market for milk. Pizza parlors and ice cream vendors are raising their prices. Starbucks has raised the price of its drinks. Milk is also weighing on profits at Cadbury Schweppes and at Kraft Foods’ cheese unit.

What is unusual, and somewhat confusing, about the milk boom compared with other booming commodities is that milk is not like oil: You cannot stick it in barrels and stockpile it. It goes sour. Even in powder form, the most commoditized version, milk has a shelf life. As a result, only about 7 percent of all the milk produced globally is traded across borders. The rest is consumed in domestic markets, which are protected by geography and just as often by tariffs or subsidies.

Big buyers like chocolate makers and grocery stores buy their milk under long-term contracts and so can smooth out sudden spikes or dips in prices. Thus, the full effect of the global shortage varies from country to country, and not all consumers are yet suffering the full impact.

But because of the local nature of the market, there is little spare capacity. In the past, the world could always count on the United States and Europe to fill shortages by exporting some of their subsidized stockpiles of cheese, butter and milk powder. But the United States has drawn down its butter mountain and other stockpiles; the same is true of the European Union, which started cutting dairy subsidies in 1993 and will finish this year. Rising dairy demand in the United States and among the European Union’s new members, moreover, is draining supplies. As a result, Mr. Hemme said, “This storage capacity is empty now.”

At the same time, rising demand for biofuels is pushing up the price of corn and other grains, which is what farmers in the United States, Europe, Canada and Japan feed their cows instead of grass. Rising feed costs help to push milk prices even higher.