Jerry Yang is the $1.8 billion man. The stock market thinks Yahoo is worth that much more without Yang at the helm.

That’s approximately how much the market capitalization of Yahoo’s stock went up this morning, with the first trade after last night’s announcement that Yang would be stepping down as CEO. The shares were up nearly 12 percent in early morning trading. They opened at $11.94, compared to a close of $10.63 last night. (The $1.31 difference X 1.4 billion shares outstanding = $1.83 billion)

With Yang gone, the prospects of a renewed deal with Microsoft (at least on the search advertising front) are now greater. So are the prospects of finding someone who can take Yahoo, and hopefully it’s stock, in a new direction

The question is: Can Yahoo pick a CEO who will add more than that to Yahoo’s market cap? I guess Mark Cuban is out of the running.