That answer always stretched credulity, since it asked us to believe that the Hong Kong listing rules are superior in operation to those of the US. It also flew in the face of observed market practice, which is littered with examples of blatant selective disclosure.

The release of last week's guide provides a belated, though tacit, admission that the Hong Kong rules are inadequate to cope with the complexities of these questions. The booklet, we may surmise, also reflects confusion on the part of listed firms over their disclosure obligations and a consequent demand for more overt guidance from the regulator.

Clearly, an evolution is in process. The US reforms have put the importance of a level informational playing field at the top of the shareholder agenda. Listed companies in Hong Kong may be keen to embrace the new spirit of the times but are unsure how.

Do they continue to hold briefings for stock analysts and institutional shareholders, while excluding other shareholders and the public? If briefings are opened to all-comers, do they continue to hold private meetings with analysts and investors and, if so, what can they say and what must they not say?

The US regulatory system has its own peculiarities and may not be suitable for wholesale adoption elsewhere. Yet the differences between the US and Hong Kong approaches in this instance are telling.

Most striking is the absence from the Hong Kong guide, and its accompanying press release, of any recognition that selective disclosure in this market is a problem. Indeed, it fails to acknowledge that such transgressions occur at all.

The preamble to the SEC's final rule release stated bluntly: '[W]e have become increasingly concerned about the selective disclosure of material information by issuers . . . many issuers are disclosing important non-public information, such as advance warnings of earnings results, to securities analysts or selected institutional investors or both, before making full disclosure of the same information to the public.

'Where this has happened, those who were privy to the information beforehand were able to make a profit or avoid a loss at the expense of those kept in the dark. We believe that the practice of selective disclosure leads to a loss of investor confidence in the integrity of our capital markets.'

It is a small detail, perhaps, but revealing. The SEC release reflects a vibrant public debate and the willingness of a regulator - under resolute former chairman Arthur Levitt - to confront market failings and act on a point of principle.

By contrast, Hong Kong's pronouncement on the issue is late, unapologetic and largely anodyne. SAR regulators have long been criticised for being overly passive, and this document reinforces that impression.

Still, the guide is a step forward, in that it illuminates some of the thinking behind the rules. That should at least help reassure companies that want to communicate but are concerned over potential infringements.

One of the fears raised by Reg FD was that companies would be so nervous of breaking the rules that they would simply clam up, stemming the flow of information to the market.

In fact, many of these concerns were red herrings. Companies are in breach of Reg FD only if they act intentionally or recklessly. Those that make selective disclosures unintentionally have 24 hours to correct them.

So the idea that an inadvertent slip of the tongue could land a company in hot water is far-fetched. That assumes, of course, that the rules are applied with common sense. In this respect, SAR-listed companies may be right to be wary, since the exchange's actions have sometimes appeared arbitrary and difficult to understand.

One of the most interesting deviations between the Hong Kong and US approaches is in their treatment of the media.

In a section on 'Questions from journalists', the Hong Kong guidelines state that questions from reporters on market rumours should be met with 'no comment'.

Where sufficient price-sensitive information has been leaked for the reported story to be broadly accurate, an issuer should make an announcement to guarantee that the correct information is widely available.

The guide then continues with this remarkable piece of advice: 'This is preferable to attempting to refute or play down the story by making counter-comments to sections of the press or by writing a letter to or granting an interview with the press in question.'

In other words, companies should not deliberately misinform the market by denying media reports which were true. Indeed, a 'no comment' is preferable in these circumstances.

The exchange, which in one case last year opined that there had been 'selective dissemination of price-sensitive information to a reporter', appears to draw no distinction between investment professionals and the media.

But there is a key difference, which is recognised in the US rule. 'We believe that there is a significant difference between analysts and news reporters . . . Reporters gather information for the purpose of reporting the news and informing the public; generally, their reports are widely disseminated,' the SEC said.

'Analysts, by contrast, gather and report information to be used for securities trading; their reports are typically available to a limited, usually paying, audience.'

The exchange's approach may reflect frustration among issuers over the way information passed to analysts finds its way into newspapers.

One blue-chip finance director complained last week of some analysts 'playing reporters' - turning in search of a snippet of information that would make a headline, rather than using meetings with management as an adjunct to their own analysis. Ironically, this closely tracks one of the issues Reg FD was designed to tackle.

On Wall Street, selective disclosure spawned an incestuous web of vested interests, since analysts became dependent on 'guidance' from management for the accuracy of their earnings forecasts, and risked being shut out of the information loop if they were negative on a company.

Independence and objectivity suffered as a result but now, following the technology bust and more recently the Enron debacle, that web is unravelling. With everyone now having access to the same information, the premium may again shift to genuine valued-added analysis.

There is no reason why companies cannot still meet analysts individually, as long as material non-public information is not communicated.

This was envisaged by Reg FD, under which analysts are protected by the 'mosaic' theory (that is, they piece together non-material bits of information from the company with their own analysis to arrive at a material conclusion).

'Analysts can provide a valuable service in sifting through and extracting information that would not be significant to the ordinary investor to reach material conclusions. We do not intend, by Regulation FD, to discourage this sort of activity,' the SEC said. Sensibly policed, fair disclosure promises better and more objective analysis, and therefore a better understanding of companies. It should be embraced.