The annual eMarketer report now shows that an economic slowdown has lowered the annual forecast on advertising expenditures and growth for 2006.

The report shows an annual adjustment from $16.7 billion to $15.9 billion in 2006 and the report predicts that a slow down will occur from 30% to a smaller a 26.8% hike. The eMarketer report shows U.S online ad spending will reach $21 billion in two years and surpass $25 billion by 2010. Paid search engine placement, such as advertising with Google Adwords or Yahoo Publisher, will make up the bulk of this increase and is seen to be the most profitable form of online advertising.