AIM closing prices during 2007.

American companies looking to raise capital on the public markets are increasingly opting to file not on the Nasdaq, the storied index of dotcom success, but on the London Stock Exchange’s AIM market, which allows even early-stage companies to float their stock for quick cash without the regulatory headaches involved with a Nasdaq filing.

The number of U.S. companies listing on AIM more than doubled in 2007, from 29 in 2006 to 67 at the last count in 2007. The majority of U.S. companies listing on AIM are technology companies, and the market is particularly attractive to cleantech companies, which typically have a longer growth cycle.

The London Stock Exchange launched AIM in 1995 specifically for small-to-medium-size early-stage companies and the risk-taking investors who love them. Although it continues to be dominated by British companies, a study conducted by the London School of Economics in November 2007 noted the market has matured into a viable option for foreign companies, particularly since the dotcom bust.

The report puts the failure rate on AIM at 3 percent over the last four years, with an average monthly trading volume of more than 20 million shares, and liquidity on par with that of similarly-sized companies on other major markets, all of which increase AIM’s appeal for cleantech companies seeking to raise capital. The report also notes the total market value of overseas companies on AIM has leapt by 181.6 percent through 2006 and 2007.

A late 2006 survey of American investment banks and hedge funds by U.S. mid-market specialist investment bank Jeffries found 57 percent believed AIM would increasingly become the market of choice for cleantech companies, over the Nasdaq, in the next three years, thanks to a regulatory regime tailored to small companies and London’s long-standing familiarity with the energy sector.

If Sarbanes-Oxley regulations are relaxed, some larger companies currently looking at listing on AIM may return to the Nasdaq. For smaller companies, for which the Nasdaq is not an option, however, AIM offers the chance to list with no minimum share requirement.