“Rewriting History”, 2009-07-16 (; backlinks; similar):
We document widespread changes to the historical I/B/E/S analyst stock recommendations database.
Across 7 I/B/E/S downloads, obtained 2000–7200717ya, we find that between 6,580 (1.6%) and 97,582 (21.7%) of matched observations are different from one download to the next. The changes include alterations of recommendations, additions and deletions of records, and removal of analyst names.
These changes are nonrandom, clustering by analyst reputation, broker size and status, and recommendation boldness, and affect trading signal classifications and back-tests of 3 stylized facts: profitability of trading signals, profitability of consensus recommendation changes, and persistence in individual analyst stock-picking ability.
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