Google served more than 41 billion sponsored links on its search results pages and publisher network, marking a 14 percent increase from last August, according to new data by Nielsen//NetRatings' AdRelevance unit.

Yahoo served about half as many sponsored search links--23.2 billion--last month, but that figure represents a 21 percent increase from August, when it served 19.2 billion links. The data includes sponsored links on Google Web Search and Google's publisher network, but excludes Froogle, Image Search and other Google properties; likewise, the data includes ads served on Yahoo Search and Yahoo's publisher network.

While consumers' use of search engines also grew last year, the growth in paid search ads doesn't necessarily correlate with the growth in volume of searches, said Ken Cassar, chief analyst, Nielsen//NetRatings. Instead, the number of ads served depends on more complicated factors, including the nature of the terms that consumers query on.

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