Spending on search engine optimization is expected to increase by 43% this year, with 52% of companies worldwide saying they will spend more than in 2009, according to a report by Econsultancy.com Ltd. and the Search Engine Marketing Professional Organization. That compares with 9% that expect to spend less and 39% that expect to spend about the same amount of money on improving their rankings in natural search results.

9% of companies said they spent nothing on search engine optimization last year, 43% said they spent less than $25,000, and a third said they spent between $25,000 and $150,000, according to the report, State of Search Engine Marketing 2010. The report is based on an online survey of almost 1,500 advertisers and agencies in 68 countries in January and February.

For paid search, respondents said they expect to spend an average of 37% more this year, the survey found. Half of respondents said they will spend more on paid search in 2010, compared to 16% that said they will spend less. 34% expect spending on pay-per-click search ads to remain the same this year.

About 20% of companies spent at least $1 million on paid search in 2009, the report says.

By comparison, spending on social media marketing is still modest compared to SEO and paid search, according to the report. 37% of companies said the marketing budget for social media will remain the same in 2010, while 59% said budgets will increase. Only 4% said budgets will be less this year.

In 2009, 73% of companies had a budget of less than $25,000 for social media marketing, including 23% that said their budget was zero, the report says.