Google Trends: Drupal Vs Joomla

I had been researching google trends recently and tried on Joomla vs Drupal.
You can see the latest results for yourself using the following link:
http://www.google.com/trends?q=joomla%2C+drupal

One thing that really surprised me was the continous rise of popularity of Joomla while Drupal just maintained its place. However as can be seen the overall popularity of both the CMS systems is on rise.

For new comers who would be wondering why Joomla's graph starts after 2005 only, its because in 2005, the bulk of Mambo's developers left mambo and developed Joomla.
The popularity of Joomla can be attributed to its balance between key features like

1) functionality
2) flexibility
3) performance
4) quality of code
5) ease of use
6) documentation
7) user interface design
8) support and product marketing.

Having said that I think Joomla is a strong competitor to Drupal in terms of popularity.

Thanks