According to the Internet Advertising Revenue Report released Monday by the Interactive Advertising Bureau (IAB) and PricewaterhouseCoopers and reported by MediaPost, “the rate of expansion for online ad spending continued to accelerate during the second quarter, soaring 43 percent over the second quarter of 2003, which pegs the second quarter’s online ad volume at $2.37 billion, compares with a growth rate of nearly 40 percent and a volume of $4.6 billion during the first half of 2004…

Sequentially, online ad spending rose 6 percent over the first quarter of 2004, which the IAB and PWC revised downward to $2.23 billion from an earlier estimate of $2.27 billion.”

Search engine marketing accounted for $947 million or 40 percent of all online ad spending, up from only 29 percent a year earlier, making it the most important driver for online marketing growth.