Popularity of Drupal vs Joomla vs Wordpress

Sometimes it's good to put things into perspective. The popularity of Drupal is a good example. Even though there are thousands of contributed modules and it's getting hard to keep track of the new modules being added, Drupal as a whole is not as popular as other content management systems such as Joomla and Wordpress:

It seems Drupal has a lot of catching up to do. However, it's good to keep in mind that popularity is not the greatest indicator of the quality in terms of flexibility, speed and usability.