Traditionally the world looked to the United States for lessons on how to run a state-of-the-art stock market. But the decline of small-business listings suggests that America may do well to look for advice from some of its former students. Ironically, it may be the most antiquated exchange that offers the clearest guidance.

Of course, the United States is not the only global market to see a drying up of small-cap public offerings. Even exchanges that specialize in making life easy for such businesses have been struggling. By the end of 2011, the number of companies listed on London’s Alternative Investment Market was at its lowest level in seven years.

“There are tentative signs that this IPO disease has been spreading to Europe too,” says Colin Mason, a business professor at the University of Strathclyde in Glasgow and author of a report on the subject for the City of London. “Various mature markets look to be seeing this.”

Yet this IPO atrophy has not occurred everywhere. Markets in China, Australia and Poland continued to help the little guy flourish. Still, it is Hong Kong that offers the best example of how old-fashioned practices may end up promoting microcap listings. Hong Kong has been among the most active exchanges for small public offerings in recent years.

The reason for this success is likely to be complicated. While giant institutional investors dominate stock trading in the United States, retail investors play a bigger part on the Hong Kong market, accounting for about 22 percent of trading by value in the Asian market compared to less than 5 percent on the New York Stock Exchange. These individual — and usually amateur — investors are typically more willing to take a flier on riskier small companies.

Hong Kong may also get a tailwind for IPOs from the faster economic growth in Asia and also from lower costs for listing. This second factor is the preferred explanation for the exchange itself. “We adhere to a principles-based regime rather than a prescriptive, or ‘black-letter law’ approach, which is in use in the United States,” says Lorraine Chan, a senior vice president for corporate communications at Hong Kong Exchanges and Clearing Limited. “We believe our system can be applied with some flexibility in practice, resulting in lower compliance costs for issuers than that in the United States, which has the Sarbanes-Oxley Law.”