By Philip Elmer-DeWitt
January 20, 2011

Two lists by Daniel (“Deagol”) Tello, a Venezuelan blogger who keeps track of such things

The first, at right, shows the cumulative record of three-dozen Apple (AAPL) analysts — both professional and amateur — over the past four quarters.

The list looks a lot like the one we posted this morning, with the amateurs bunched at top and the pros — including some of the biggest names on Wall Street — at the bottom.

Topping it, for the second quarter in a row, is Asymco‘s Horace Dediu, a Romanian blogger whom we featured in a post last October and who was profiled on Wednesday.

Tello’s second list, below the fold, compares this quarter’s performance to last quarter’s to determine which analysts are getting better at this game and which are getting worse.

The results are striking. Not only are the amateurs out-performing the pros, but they are improving dramatically — in some cases by 60% and 70%.

On the other end of the scale, the performance of the pros who did badly last quarter seem to be deteriorating. The accuracy of two of the Street’s most famous Apple watchers — Morgan Stanley’s Katy Huberty and Bernstein’s Toni Sacconaghi — fell by 32.7% and 31.7% respectively.

A pair of Wall Street analysts came to their profession’s defense in Bloomberg’s article, suggesting that their conservatism is a function both of their rigorous training and their memory of past booms that went bust.

“Often bloggers and amateur investors are very good in bull markets but get lost in bear markets,” said Exane-BNP’s Alexander Peterc. “If some of these guys call the moment at which Apple’s fortunes begin to turn I will be impressed.”

Asymco’s Dediu is skeptical. In a piece posted Wednesday afternoon he suggests that the issue for the pros is that the institution risks becoming de-professionalized.

“The difference between professionalism and amateurism isn’t whether one is well paid or not or whether one is anointed with credentials. It’s whether one is consistently out-performing randomness (note emphasis on the consistency). … In the same way many jobs that took specialized skills became commoditized by the use of new tools or access to information, the era of DIY financial analysis is dawning.”

Below: Tello’s chart of the error reduction (or increase) over the past two quarters.

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[Follow Philip Elmer-DeWitt on Twitter @philiped]

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