Yahoo is looking for a new CEO as Jerry Yang takes his in-house guru job back (I’d like one of those jobs). Sure, he made a lot of missteps, but just how much of Yahoo’s plummeting fortunes are his fault rather than the market’s lower expectations for the growth of online advertising? I haven’t done a systematic study but here’s what a quick check shows. Since the beginning of the year—and a month before Microsoft’s offer to Yahoo affected things—Yahoo’s stock price has declined by 56.6 percent. That compares to 54.29 percent for Google. Maybe someone with more time could put together a portfolio of online ad properties to see what the overall market did. By the way, Microsoft’s share price declined by 45.72 percent over the same time period.