Davie Brown Entertainment, a unit of Omnicom Group, began polling in 2006, after talking to marketers and ad agencies about the attributes most important to them in celebrity endorsers. The company settled on seven attributes, including appeal, influence and trust. Respondents who recognize the celebrity are asked to rate him or her on each of those attributes on a six-point scale. Then their scores are averaged, and that attribute average is combined with awareness, which is weighted more heavily, to produce the Davie Brown Index.
Assigning so much weight to name recognition can yield perplexing results. Mr. Woods's index dropped only modestly, to 80.9 just before his apology from 89.2 a year earlier, in part because slightly more people were aware of him. This helped overcome a plummet in trust, to 43.7 from 68.8.
"The overall DBI number is very, very important, but we look at everything," says Jeff Chown, president of Davie Brown Entertainment's talent division.
The newest entrant on the scene, Millward Brown, rates celebrities and brands on the same scale, to identify the best marketing fit. Like the Davie Brown Index, Millward Brown's Cebra scores also emphasize familiarity, which is averaged with likability and "buzz," or media attention. Mr. Woods's Cebra score dropped only slightly, to 67 this month from 70 last September. A crash in likability, to 46 from 69, was mitigated by a surge in buzz, to 85 from 74; and a small bump in familiarity, to 70.