What Would a Combined Microsoft-Yahoo Look Like?

Microsoft’s $31 a share offer for Yahoo is made possible by Yahoo’s slumping shares (Yahoo’s stock was trading at about $31 a year ago). While Yahoo has rejected Microsoft’s entreaties in the past, with Terry Semel stepping down as chairman of the board yesterday, things might be different this time. I ran some quick, back-of-the-envelope numbers to see what a combined Microsoft-Yahoo would look like financially, and how it would compare to Google.