The largest market is the United States , where tens of thousands of beauty salons offer hair extensions. African-American women have long worn hair extensions, but the trend among women with lighter hair has been popularized by celebrity endorsements from the likes of Jessica Simpson and Paris Hilton .

Great Lengths, an Italian company and major supplier to the United States, has estimated the American retail market for hair extensions at $250 million annually, or about 3 percent of the entire hair care products market. The average price for extensions is $439, according to a 2009 survey by American Salon Magazine, although the procedure can cost several thousand dollars at elite salons.

The extension business is also growing in Europe .

An estimated 20 percent of Russian hair is used domestically, by the well coiffed of Moscow and St. Petersburg .

The blond harvest is not necessarily new, having followed an economic development path in recent decades, moving from Western Europe in the 1960s and ’70s, through Poland in the ’80s and to Ukraine and Russia after the breakup of the Soviet Union in 1991. But as more of the world’s light-haired woman have climbed the economic ladder, the search for poor blondes willing to part with their locks has become ever more difficult.

“It’s not hard to understand why people in Ukraine sell their hair a hundred times more often than people in Sweden ,” David Elman, a co-owner of Raw Virgin Hair Company, an importer based in Kiev, Ukraine, said in a telephone interview. “They are not doing it for fun. Usually, only people who have temporary financial difficulties in depressed regions sell their hair.”

Here in Mosalsk, a 16-inch braid, the shortest length a buyer will consider, fetches about $50.

Natalya N. Vinokurova, 26, grew up nearby in Yukhnov, a town where half the homes lack indoor plumbing and the average monthly wage is about $300. What little cash-crop agriculture there once was collapsed with the Soviet Union.

But Ms. Vinokurova cultivated something with market value: strawberry blond hair that hung to her waist before she sold it.

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“I wore it in a braid, a ponytail, different ways,” she said. “But I got sick of it, and all the other girls have short hair, so I cut it,” and then sold it, she said with a shrug. She now wears a bob and has no immediate plans to grow it to a marketable length, which she said would take years.

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Mr. Kuznetsov’s company here, Belli Capelli, which processes human hair into extension kits, is the largest business of its type in Russia, with annual revenue of about $16 million.

Kicking mud from his boots, he clambered into a Land Rover to tour the buildings here and in a neighboring town where a few dozen employees wash, dye and comb hair, then sort it by hue and length. At one sorting table, where about 500 braids were laid out, he stopped to extol the quality of his product. The best hair, he said, is honey-hued, changes color in the light and is soft to the touch.

“This is capitalism,” he said. “The people with money want to distinguish themselves from the people with no money. Why does one woman sell her hair to another? The person with money wants to look better than the person without money.”

American customers are typically unconcerned about the origins of extensions, other than to ask if they are hygienic, said Ron Landzaat, founder of Hair Extensions Guide, a trade group in Santa Rosa, Calif., who said the hair was sterilized by boiling it.

“They are concerned about their looks more than anything else,” Mr. Landzaat said by telephone.

Obtaining adequate supplies is the industry’s biggest challenge.

Great Lengths, the Italian supplier to the American market, obtains hair that women have ritualistically donated to temples in India, and says it can be dyed to match most hair types. Others in the business, including Mr. Kuznetsov, say European hair is a better option for women with light hair, and so is prized.

Russian factory towns in the Ural Mountains , about 900 miles east of Mosalsk, became such contested territory among hair buyers that in 2006 one was shot in a dispute with another, suggesting Russian organized crime involvement, the newspaper Kommersant reported.

Although Mr. Kuznetsov has no local rivals that he knows of, he keeps a security guard posted at the entrance to his storeroom. The milk crates, filled with the hair of thousands of women and sorted by categories including “Southern Russian” and “Russian Gold,” might make an alluring target for a heist.

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Most hair comes from buyers who roam the rougher parts of Russia, Ukraine and other former Soviet states, posting fliers on utility poles offering money for hair. In Belarus , President Aleksandr G. Lukashenko , a staunch nationalist, has placed such tight controls on small entrepreneurs that the trade is all but impossible, to the regret of those in the business, because the country is poor and has an abundance of blond women.

Generally, about 70 percent of the hair bought in Russia comes from locks kept at home from previous haircuts. Some Ukrainian and Russian women, for example, traditionally cut their hair after the birth of their first child, and may decide only years later to sell it. In areas of dire poverty, it is a final resource to tap in times of desperation.

The rest is bought, often after some haggling, directly from the head of the seller, who then gets a haircut on the spot. As a courtesy, in Russia, the deal is nearly always done in a salon so a hairdresser can cut carefully.