Search marketing makes up 57% of UK online ad spend

"Marketers in the UK say search marketing is the most efficient way to generate leads - so it's no wonder that search marketing accounts for the lion's share of online ad spending compared with other formats, making up more than half (57 percent) of the online advertising dollar (so to speak) in the UK"
Source: MarketingVox, 14th January 2008, citing (ultimately) PwC/IAB research