March 12, 2007

Are Thousands of Stock Analysts Rewriting Their Track Records? Could Very Well Be

Megan McArdle, one of those sitting in for Instapundit for a few days, calls attention to this stunner (I/B/E/S is the “Institutional Brokers Estimate System“):

Comparing two snapshots of the entire historical I/B/E/S database of research analyst stock recommendations, taken in 2002 and 2004 but each covering the same time period 1993-2002, we identify tens of thousands of changes which collectively call into question the principle of replicability of empirical research. The changes are of four types: 1) The non-random removal of 19,904 analyst names from historic recommendations (“anonymizations”); 2) the addition of 19,204 new records that were not previously part of the database; 3) the removal of 4,923 records that had been in the data; and 4) alterations to 10,698 historical recommendation levels. In total, we document 54,729 ex post changes to a database originally containing 280,463 observations.

Maybe there’s a perfectly acceptable explanation for an after-the-fact alteration rate of almost 20%, but until I hear it, it’s hard not to think that there is quite the contingent of “grown up” David Lightmans (the main character in the 1983 movie “War Games,” played by Matthew Broderick, who, among other things, hacked into his high school’s computer system and changed his grades) systematically rewriting their history. And I’d not only like to ask the Watergate question (“What did they know and when did they know it?”) of industry CEOs during that period, I’d like to know (again, if this really is abusive history rewriting) what they’re going to do to stop it now — AND to put things back to where they were.


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