Eric Schmidt's choice of Susan's mid-range revenue estimate proved unduly conservative. By the end of the contract's first year, we were far above the highest projections. Part of that success may have been attributable to a small shift made by an enterprising engineer. The day after the deal went live, John Bauer added code that boldfaced the keyword a user had searched for when it appeared in an ad, making it obvious that the ad was relevant. That single improvement increased clickthrough rates by four hundred percent. One engineer. One change. Four hundred percent.