How do we know this? Well, MSN Money . . . Microsoft's online investor resource . . . has a handy 'insider trading' page that allows users to track the stock moves of corporate executives, presumably with an eye towards profiting from what the bosses know but the overall market doesn't.

But unlike Flavin's divestment from Fyffes just before a profits warning (and the dotcom bust), this kind of insider trading isn't illegal. In fact, there's a whole subculture of retail investors who actively monitor trades by insiders in order to emulate their success.

To wit, anybody invested in Microsoft watching Gates's trading activity would have been wise to reduce their positions along with the chairman, as the software giant has struggled along with the broader market in the last two weeks. At time of writing, MSFT was down close to 3% on Gates's sale price.

That result should come as no surprise.

According to research by Nejat Seyhun, an insider trading expert at the University of Michigan, when executives buy shares in their own companies, the stock beats the market by an average 8.9% over the next year. When they sell, the stock underperforms by 5.4%.

Obviously, insiders know something that the rest of us don't . . . and they capitalise on it. The difference between Flavin and Gates, however, is whether the market sensitive information has become public knowledge. In Flavin's case, the public was in the dark about Fyffes when he cashed out.

Insiders do have to report their trades to the relevant regulator as well as the exchange . . . take a look at the Irish Stock Exchange's company announcements to get a flavour . . . so theoretically the retail investor is in the loop.

But who actually knows why Bill Gates was selling? Moreover, who actually thinks anybody apart from maybe a dozen guys at Microsoft knows enough to trade in Microsoft on an equal footing with the founder? In legal terms, the difference between Flavin and every other executive is clear enough; in practical terms, the distinction is a bit hazier.