Why is PPC spend so much higher than SEO spend?

The following article provides lots of good numbers in the PPC vs SEO spend debate. The basic premis is that if Natural listings have higher visibility and click through rates – why is the spend towards PPC disproportionate? There is the suggestion that clients understand PPC better and find it easier to control. I think some of the more obvious answers are not discussed in the article or in the top few comments I skimmed. These are namely that PPC is immediate, allowing messages to be tested and changed quickly and efficiently to support new initiatives as well as old. Also PPC allows you to have presence for thousands of keywords while SEO cannot promise this breadth. The main reason of course is the ability to track conversions in real time and optimise for these. We will start testing DART’s SEO tracking in Q1 2009 – this could make all the difference… but I am not holding my breath… Check out the article and see what you think.

http://www.seomoz.org/blog/the-disconnect-in-ppc-vs-seo-spending