WAKEFIELD, Massachusetts: Search marketing expenditure will grow in value from $14.7 billion (€11.2bn; £10.4bn) in 2009 to $26.1bn in 2013 in North America, reports a study by the Search Engine Marketing Professional Organization and Radar Research.

A total of $13.5bn was spent on search marketing in the region in 2008, with 88% of this total being directed towards paid search, and just 11% diverted to search engine optimisation.

In terms of paid placement, "search media firms" were responsible for just over $10.7bn in revenues last year, compared with $804.7m in expenditure delivered "in-house" from advertisers, and an outlay of $351.8m by "SEM agencies".

However, eMarketer's senior analyst David Hallerman argues that search engine optimisation will become increasingly important in the future.

This is because web users "prefer organic listings to paid search", either because they are seen as more "relevant" or "acceptable" than advertising, meaning preferable positions in non-paid for listings will achieve greater clickthroughs rates than search ads.

A report from the Association of Online Publishers in the UK has also forecast that online publishers' digital revenues will rise by 16% this year to £928m, from £800m in 2008.

This total includes online advertising, subscriptions, sponsorship and e-commerce, and 63% of online publishers plan to increase their digital outlay this year, compared with 7% who will cut back.

Data sourced from eMarketer/Brand Republic; additional content by WARC staff