Greenspan was so committed to strategic verbal ambiguity in his stewardship of the US central bank that the Federal Reserve Bank of Dallas, its subsidiary, devoted an entire section of its website to honouring "Greenspeak" . . . the peculiar mix of pithy aphorism and meaningless waffle that made up the his policy speeches.

Well, the sun appears to be setting on the Greenspan era now that German Bundesbank president Axel Weber has indicated that the European Central Bank will stop using "code words" in its statements about the direction and timing of interest rate changes.

Since last summer, a predictable pattern of ECB statements and rate rises has emerged. First ECB president Jean-Claude Trichet says the bank will "monitor very carefully" inflation risks.

The next month he escalates to "strong vigilance" . . . and the month after that he raises borrowing rates by a quarter-point.

In other words, the code had ceased to be a code.

When Trichet said "strong vigilance", nobody had to read the tea leaves . . . it was obvious that he meant rates were going up in a month.

Instead of signalling probable developments under the radar, he was broadcasting on an open frequency. Ironically, that chimes nicely with the ECB's wish to foster more predictability around monetary policy.

Yet the key to Greenspan's effectiveness as a guru, if not as a central banker, was arguably the unpredictability of his ambiguity. With every utterance there was another imponderable to ponder, another non-committal judgment. Predictable ambiguity, though, just becomes a form of clarity after a while, leaving no room for hedging.

Once they got a read on Trichet, market players just started pricing in the rate rises a month or two early.

Weber says the bank will start using plainer language after the current cycle of tightening is complete, eschewing the rhetoric of "broad hints" the bank has used recently and focusing on more concrete mediumterm analysis, but it's hard to see how the language could be plainer than it already is.

Of course, Weber declined to give any broad hints . . . or to speak plainly . . . about when that tightening cycle would actually end.