Workers in developing countries all over the world are becoming more aware of pay elsewhere through the Internet and the use of social media like Facebook, increasing the pressure for higher wages, Mr. Rockowitz said.

Li & Fung handles about 4 percent of American retailers’ imports from China of virtually all kinds of consumer goods, according to investment analysts. The exception is electronics, which tend to be imported directly to the United States by other companies like Apple.

Mr. Rockowitz and other executives predict that the extremely high concentration of factories in southeastern China near Hong Kong will give way to a dispersal across the country in the next five years. Workers are becoming much more reluctant to spend up to three days on buses and trains from the interior to reach coastal factories, particularly when the growth of domestic spending in China is creating more jobs in the interior.

Even the recent opening of high-speed rail routes that cut travel times up to 80 percent has not been enough to revive the flow of migrants. “They don’t have to take a 1,000-mile trip to the coast — there’s a shortage of people, unbelievable,” said Douglas Hsu, the chairman and chief executive of the Far Eastern Group, a big Taiwanese multinational with extensive investments in mainland China.

And wages in China’s interior have been rising even faster in percentage terms than in coastal provinces, steadily narrowing what was once a pattern of much higher wages in coastal export zones.

Many companies have another reason for staying in China these days: that is where their sales are growing fastest. “If the market is in China, which in many cases it now is, there’s much less incentive to move,” said Charles Oliver, the senior partner of GCiS China, a market research company in Shanghai.

China has become the world’s largest market for a long list of products, like cars and steel. Producing and selling in China protects companies from later facing “Buy Chinese” policies, antidumping cases or other Chinese import restrictions.