European Central Bank researchers do not think much of Alan Greenspan's delphic pronouncements on the US economy during his 18 years at the helm of the Federal Reserve.

According to research published in Frankfurt by the ECB, Greenspan's success in dealing with the vicissitudes of the US economy was probably due more to luck than skill.

Greenspan couched his statements on the economy in such confusing language that they baffled the best brains on Wall Street and Capitol Hill.

Greenspan mocked his own speaking style in 1988 when he said: "I guess I should warn you, if I turn out to be particularly clear, you've probably misunderstood what I said."

The Fed chairman was lauded for his handling of the Black Monday stock market crash that occurred shortly after he first became chairman in 1987, as well as for his stewardship of the internet-driven, dot.com boom of the late 1990s.

However, this expansion culminated in the bubble bursting in March 2000, and a recession in 2001-2002.

From 2001 until his retirement in 2006, he was increasingly criticised for statements seen as overstepping the mark regarding the Fed's traditional role in setting monetary policy. He was viewed by others as overly supportive of the policies of President George W Bush - and of policies seen as leading to a housing bubble that continues to have a negative impact on the US economy.

Greenspan was, nonetheless, considered during that time to be the leading authority on US domestic economic and monetary policy, and his active influence continues to this day. The ECB researchers, how- ever, challenge the idea that Greenspan had superhuman powers.

"Our evidence points toward a dominant role played by good luck in fostering the more stable macro-economic environment of the last two decades," said researchers Luca Benati and Haroon Mumtaz of the ECB and the Bank of England.

This means that if the US faced another economic shock similar to the sharp rise in oil prices during the 1970s, today's Fed policymakers may not be much better placed to cope, the researchers said.

The ECB said the researchers' findings do not reflect its views.