Firefox: Dramatic change in release version patterns

History of Firefox starts in 2002, when a new flavor of Mozilla was released under the name Phoenix. With the release of 0.6 it was renamed as as Mozilla Firebird, but it lasted only for two releases. This most popular name "Firefox" was introduced with the 0.8 release, and it continues as of the time of this post. Initially, Firefox made a major release every two years with minor releases in between.

Two yearly
Version 0.1 - 2002
Version 1.0 - 2004
Version 2.0 - 2006
Version 3.0 - 2008

However in 2011, the release pattern completely changed which resulted in major releases within every one or two months duration as shown below.

 Monthly
 4.0 - 2011/03
 5.0 - 2011/06
 6.0 - 2011/08
 7.0 - 2011/09
 8.0 - 2011/11
 9.0 - 2011/12
10.0 - 2012/01

Particularly within first 6 months of 2013, there were 5 major releases (18.0 to 22.0).

So it is worth finding the reasons for this dramatic change in the release process. As per my understanding, this change had a direct relationship with the new comer Chrome browser in 2008. First major release of Chrome (1.0) was done few months after the Firefox 3.0 release. However in early 2010 Chrome started making major releases every few months and when Firefox 4.0 was out in 2011 March, latest Chrome release available was 10.0.

Mozilla team seems to have identified a potential problem when introducing Firefox over Chrome; release number of Chrome is way beyond Firefox (which may look as related to number years of existence by someone). So Firefox releasing pattern also seemed to follow this fact track, but the latest Firefox version 22.0 while Chrome is 30.

As a side note, I think it is worth mentioning a summary on this battle.
When Firefox was so popular in around 2006, Google funded Firefox and in return became the Firefox's default search engine. Interestingly, 2008 born Google owned Chrome became the most popular browser sending once most popular Firefox into the third position behind Internet Explorer. I personally believe Google did it perfectly, they had a great plan and won the battle well ahead where as Firefox team could not resist a lot.