Erick Schonfeld at TechCrunch published an estimate on the current slowdown in advertising revenue generated by Google, Yahoo, Microsoft, and AOL. The sequential growth rate was 12.7 percent in the fourth quarter of 2007, down to 2.8 percent in the first quarter of 2008, 1.1 percent in the second quarter and down to an estimated 0.6 percent in the third quarter.

Even without this analysis, it’s pretty clear that the online advertising industry as a whole has definitely decreased in recent quarters. Google however, is the winner over Yahoo, Microsoft, and AOL clearly demonstrating the effectiveness of their Adwords network.